Luas management is trying to “divide and conquer” staff as it attempts to get three grades of workers back to talks tomorrow to end the dispute, said Siptu.
But drivers remain defiant and are threatening to announce further 24-hour and 48-hour strikes before considering a ballot for an all-out work stoppage next week.
Ticket inspectors and their supervisors are due to attend talks to end the row over pay rises and better working conditions at the Workplace Relations Commission tomorrow.
Control room staff, of whom there are just 16, met last night to discuss the possibility of joining the discussions.
Talks broke down when this group demanded a 20pc pay rise upfront, backdated to 2014, last Monday.
Discussions with drivers also failed after Luas operator Transdev rejected their revised pay claim, for what Siptu said was a pay increase of 27pc over five years – or between 5pc and 6pc a year.
It is understood that the two groups that are definitely attending talks are seeking pay increases in the region of 4pc a year over five years. Transdev has said it will consider pay increases of 1pc to 3pc.
“If there are three grades there tomorrow, it’s obviously better than none,” said a spokeswoman for Transdev.
Kieran Mulvey, who is hosting the talks, said two of the groups had indicated to the company that they were willing to negotiate around parameters that meant “both could probably come to some agreement”.
He said that drivers and the company were still “significantly far apart”, but that “there’s a bit of time” before any escalation of the dispute materialises.
The mediator said the dispute has to be settled “sooner rather than later”, but it was not going to be achieved on the picket lines or on the airwaves, but in the rooms of the Workplace Relations Commission.
“We feel there’s a bit of time still, before any escalation of this dispute beyond what’s already been announced, for wise counsel to prevail on both sides,” he said.
He said Siptu’s decision to back an all-out strike probably indicates how “seriously” the union’s General President Jack O’Connor views the situation.
“I would hope that it is more or less a shot across everybody’s bows,” he said.
“There will be a long time before that comes about – and I hope it doesn’t come about.”
Siptu official Owen Reidy said he believed there was an attempt by Transdev management to “divide and conquer” staff, but said there was as much of a divide between staff’s demands as there ever was.
“All of the four groups want to come to talks, but the employer seems to be picking who it wants to talk to.”