The Minister for Transport, Mr Brennan, is to meet union representatives from CIÉ this afternoon to discuss his plans to break-up the transport group.
SIPTU and the National Bus and Railworkers Union (NBRU) will attend the meeting, at which they are expected to voice their continuing opposition to the move to split CIÉ into separate companies and to introducing competition on some Dublin Bus routes.
Workers at Dublin Bus, Bus Éireann and Iarnrod Éireann protested against the minister's plans last July, holding a "no fares" day where they refused to charge passengers for travelling.
The company threatened to delay a pay increase to workers for a month following the dispute, which was estimated to have cost €1.2 million in lost revenue.
Withholding the payrise due under the Sustaining Progress agreement until November will save CIÉ around €300,000 a week for four weeks.
The unions are to contest the move and the matter is now expected to be referred to the Labour Relations Commission.
Mr Brennan said last week that funding for Irish Rail must be linked to fundamental reform of the company. He told The Irish Timeshe was "seriously concerned" about the financial situation in the company, with State subvention rising to €175 million last year from €169 million in the previous year.
The minister also reiterated his commitment to the break-up plan and to introducing competition into the Dublin bus market. He said he expected this to happen some time next year.