Up to 70 people are likely to have been involved in the IRA preparing for and carrying out the ambush in which two senior RUC officers were killed, it has emerged at the Smithwick Tribunal.
Retired British Army Brigadier Ian Liles, who worked as an intelligence officer along the border, also confirmed that radio traffic between IRA members started between 11.30am and noon on the day the two RUC officers were killed.
This was several hours before Chief Supt Harry Breen and Supt Bob Buchanan left Newry RUC Station.
The Smithwick Tribunal is investigating claims a garda passed information to the IRA about the visit of the two RUC men to Dundalk on the afternoon of 20 March 1989, allowing them time to set up an ambush.
The two officers died in the attack, just minutes after leaving a meeting in Dundalk Garda Station.
Three former garda sergeants - Owen Corrigan, Finbarr Hickey and Leo Colton - are being investigated. All deny claims that they passed on information to the IRA.
Brigadier Liles originally gave his evidence to the tribunal in private.
Following discussions with the British Ministry of Defence, a transcript of his evidence was read into the record today by Counsel Dara Hayes, with what he said were three "minor" changes made at the request of the ministry.
The witness took up his role as intelligence officer with 3 Brigade several weeks after the RUC men were murdered.
He said there was analysis of information gathered in the aftermath of the killings. It was his view that around 70 people would have been involved altogether in the attack.
This would range from "beaters" who would have gone around beating the hedges near where the weapons were stored to check for British soldiers before the arms were taken out, to spotters looking out for patrols in areas, to the actual men involved in the shooting.
He also said that the British security forces started to pick up an increase in radio traffic from 11.30am that day that went on until after the two RUC men were killed at about 3.50pm.
Brigadier Liles said it was his view this meant that the actual operation began earlier in the morning, possibly around 10am.
The witness also told the tribunal that he was not aware of "technical information", which suggested there was a phone contact from Dundalk Garda Station to a member of IRA on the morning of the ambush.
Such a claim had been made by journalist Toby Harnden in his book "Bandit Country".
RUC chief did not trust Dundalk gardaí
The retired brigadier confirmed that he knew the late RUC Chief Superintendent, Frank Murray, who was the head of the Special Branch in the border area.
He said Mr Murray did not trust gardaí in Dundalk because he believed they leaked information to the IRA. The witness said Mr Murray would always have preferred to deal with gardaí in Dublin instead.
The British Army had limited intelligence that said that the northern command of the IRA were aware of the attack in some form. It was possible, he said, that this meant they were aware an attack would be mounted against a senior RUC figure at some time.
There was also intelligence that gardaí in Dundalk, whom the witness said had a difficult job to do dealing with terrorists, were sometimes subject to intimidation from the IRA. This would take the form of "stay out of our way or your family will get it" type threat.
Dara Hayes, Counsel for the Tribunal, who read out the transcripts in the public record, said that under cross-examination by Michael Durack, Counsel for the Garda Commissioner, the witness said the radio traffic from the IRA started at around 11.30am and grew into a "crescendo".
The RUC officers did not leave Newry RUC station until around 1.30pm and the ambush did not happen until around 3.50pm, so Mr Durack wanted to know why information had not been passed on.
Brigadier Liles said he would have presumed it was, but he pointed out that they would not have known the RUC men were heading to Dundalk, nor would they have known a major attack was planned, nor could they have known where something might happen.
It was also an issue that this was in an era before widespread use of computers and e-mails so the events were not reported in "real time".
The two RUC officers were travelling up the Edenappa Road when they were ambushed and killed, having turned off the main Dundalk to Newry road.
The brigadier told the Tribunal that he would not have used that road ever. He said he would have used the main road "at great speed".
Gardaí and IRA member share same name
It is emerged at the Smithwick Tribunal that there is a member of the IRA who shares the same name as one of the former gardaí under investigation.
During a heated row today, counsel for retired Det Sgt Owen Corrigan, Jim O'Callaghan, said there was a man who shared the same name as his client and who was a member of the IRA during the 1970s, 1980s and 1990s.
His comments came in a row over whether a summary of intelligence reports written by Mr Corrigan during his career should be read into the record at the Smithwick Tribunal.
Earlier in the week, counsel for the Tribunal, Mary Laverty, said the information would be read into the record today.
However, today another senior counsel for the Tribunal, Justin Dillon, said the information would not be read into the record.
There was, he said, no doubt that Mr Corrigan had been a diligent servant of the State and the tribunal had heard about intelligence matters he passed on. He said there was no value to reading the information into the record.
Mr Dillon also strongly objected to the fact that the Garda Commissioner had passed on information sought by the Tribunal to Mr Corrigan's legal team. The information about the intelligence reports written by Mr Corrigan, raised serious issues about details being passed onto third parties, he said.
Counsel for the Tribunal went on to raise concerns he had about the similarity between questioning of witnesses by the legal teams for the Garda Commissioner and Mr Corrigan.
He said questions were being asked by the Commissioner's team that were designed to support Mr Corrigan. He said gardaí had effectively "cut loose" on the other former members being investigated.
As regards the person with the same name, that was an issue that would be addressed, said Mr Dillon.
Mr O'Callaghan said the intelligence information was of great benefit to his client. There is information there that his client saved the lives of RUC offices and that is relevant.
He said the Garda Commissioner's legal team and himself were on similar view that there was no evidence against his client "and Mr Dillon is going to have to face up to that".
Counsel for the Commissioner, Michael Durack, said it was common practice that officers would be able to see information they had written and there was no issue with providing Mr Corrigan with copies of intelligence reports he had written.
The Commissioner's view is that there was no evidence of collusion in relation to ambush or indeed anywhere else, he said.
Judge Smithwick said the issue would be discussed next week.
