An efficiency review of the Dublin Fire Brigade Ambulance service has been jointly ordered by Dublin City Council and the Health Service Executive.
It follows a long-running dispute between the council and the HSE over the provision of ambulance services in the capital.
The HSE pays €10m a year to Dublin City Council, which runs the fire service on behalf of the four Dublin local authorities.
Last year the HSE was reported to be considering phasing out fire brigade ambulances believing that it could save nearly €3m a year as firefighters are paid more than HSE ambulance staff.
The HSE was also reported to be concerned over the lack of control over the service as the Fire Brigade is also not subject to checks by the Health Information and Quality Authority.
However, Dublin City Council believes the HSE payment does not cover the cost.
The Fire Brigade provides 12 ambulances that cover the central Dublin area, while the HSE provides ambulance cover in outlying areas such as north county Dublin and Tallaght.
Brendan O'Brien national organiser of SIPTU members in the Fire Brigade said they would be concerned about any downgrading of the 100-year-old service.
He said all 840 firefighters are also trained paramedics under the current system, which is important for dealing with serious incidents - like the Wellington Quay - bus crash involving multiple casualties.
"When the LUAS crash happened on Abbey Street we had 35 trained paramedics on the scene within four minutes. We wouldn't like to see this review resulting in any reduction of this high level of service", he said.
The review announced jointly by the HSE and Dublin City Council will compare each ambulance service to identify "the optimal model for the provision of emergency ambulance services and patient care taking account of quality, patient safety, and value for money"
It will be completed by the end of May.