There are mounting fears of increased transport disruption tomorrow amid reports that staff at Dublin Bus and Iarnród Éireann may join a protest at Leinster House in support of Bus Éireann workers.
1,900 Bus Éireann staff have been on strike since last Friday in a dispute over cuts to pay and conditions, which management insists are essential to avert the prospect of insolvency at the loss-making company.
Minister for Transport Shane Ross has repeatedly refused to get involved in the dispute, saying it is for Bus Éireann management and unions to resolve the row between themselves.
However, he is due to appear before the Oireachtas Committee on Transport Tourism and Sport tomorrow afternoon, and a protest in support of Bus Éireann workers is being organised outside Leinster House to coincide with that.
Unions accept that they do not have a trade dispute with Dublin Bus or Iarnród Éireann - and their official position is that workers who are rostered on duty at those companies should report for work as normal.
However, union sources say there is a strong possibility that some members in Dublin Bus and Iarnród Éireann may leave work to support their Bus Éireann colleagues, because they fear that if cuts are pushed through in the regional bus company, they could spread to the other CIÉ group firms.
That could disrupt some Iarnród Éireann or Dublin Bus services - though the scale of potential disruption is impossible to calculate at this point.
Neither company has been notified of any potential industrial action.
Yesterday, SIPTU announced that it plans to ballot members in Dublin Bus and Iarnród Éireann for industrial action "in sympathy with and in support of their colleagues in Bus Éireann".
At tomorrow's Oireachtas Transport Committee meeting, Mr Ross is expected to say that he does not have a "ministerial magic wand" that can resolve the Bus Éireann dispute, and will not be dictating to management and unions about their internal issues.
He will say that a deal can be done, though it will require imagination, flexibility and compromise.
He will point to total taxpayer funding to the company of €230m, across the public service obligation routes, school transport, free travel and capital expenditure programmes.
He will also reiterate that he is committed to a review of public transport policy which will allow for an in-depth consideration of all relevant issues facing transport in the future.
Tomorrow will be the sixth day of the nationwide bus strike, which is costing the company €500,000 a day.
There are fears that if the dispute is not resolved soon, the company may have to seek the protection of the courts through the appointment of an examiner, though so far, the company has said that option is not on the table.
Meanwhile Unite, which represents around 100 craft workers in Bus Éireann, has said that it will make its €40m strike fund available to support its members in the dispute.