The Irish Locomotive Drivers' Association is expected to announce on Monday a series of one-day strikes in support of eight members on disciplinary charges.
This follows clarifications from the Labour Court endorsing Iarnrod Eireann's position that ILDA is not entitled to represent drivers at appeals tribunals.
Yesterday the secretary of the ATGWU's ILDA branch, Mr Brendan Ogle, described the court's decision as "a nonsense which flies in the face of a number of precedents relating to the operation of these procedures.
"The court has confused individual rights to representation with the very separate right to collective bargaining."
He said three of the eight drivers were at a stage in the disciplinary process where they had either to appeal to a senior manager or the appeals tribunal. No appeal to a senior manager had ever been successful.
Asking ILDA drivers to be represented by SIPTU or the National Bus and Railworkers' Union, which they had left three years ago, was "tantamount to asking them to eat their own dirt".
Over the weekend the ILDA branch committee "will consider what dates we will fix for industrial action and we will also communicate with the ATGWU and seek legal advice on the manner in which the court has proceeded", he said.
Iarnrod Eireann's human resources manager, Mr John Keenan, said this was another example "of Mr Ogle receiving a decision from a statutory body he disagrees with and once more threatening our customers with disruption. Clearly he is not prepared to take No for an answer. "The implication is that our services will continue to be threatened until he gets what he wants, and that is unacceptable".
It was unclear last night how much notice ILDA will give of industrial action. As it is resuming the dispute suspended last May it may argue that a full week's strike notice is not required.
Whenever action does take place it is likely to be on an "escalator" basis, with the frequency and duration of disruption increasing as the weeks go by.
When the strike was deferred it was on the basis that the ICTU would investigate the ATGWU's right to represent train-drivers through its new ILDA branch and that the court would assess if the company was operating its disciplinary procedures fairly.
The ICTU found against the ATGWU, and now the Labour Court appears to have found largely in favour of the company.
A major upset for ILDA is the failure of the court to investigate the individual grievances of its eight disciplined members. However, Mr Ogle has been told cases can be referred to the court later if drivers are unhappy with the outcome.
