A deadline has been set of February 20th
There are fears any strike action at Bus Éireann could lead to solidarity action by other CIE companies.
Bus Éireann SIPTU workers are set to engage in an all-out strike from Monday February 20th.
But they say they will engage in talks with management once the company removes its threat to unilaterally change workers' terms and conditions of employment.
While SIPTU members in Dublin Bus and Irish Rail have pledged to display "solidarity" with their colleagues in Bus Éireann.
It followed a meeting Friday between SIPTU representatives of members in Irish Rail, Dublin Bus and Bus Éireann.
SIPTU sector organiser, Willie Noone, said: "At the meeting the clear consensus was that there is a strong commitment by SIPTU members across these companies to display solidarity with workers in Bus Éireann, whose conditions of employment are currently under vicious attack.
"It was noted that in circumstances where management goes ahead and unilaterally introduces cuts to workers pay, terms and conditions on 20th February, that all our members in Bus Éireann, except for school bus drivers, will be in an indefinite strike from that date.
"It was also highlighted that the likelihood of the dispute spreading to school bus drivers, and the consequential adverse impact this would have to rural areas in particular, is increasing."
He added: "The representatives of our members in Irish Rail and Dublin Bus have indicated that they are willing to take whatever appropriate actions are necessary to support their colleagues in Bus Éireann, as they all are members of CIE companies and have corresponding conditions of employment and work locations."
While representatives at Dublin Bus are meeting on Monday to finalise arrangements for a separate strike ballot.
SIPTU say this appears to be "overwhelmingly supported."
The NBRU claims the failure of Dublin Bus to honour the terms of a WRC document from September 2016 - specifically in not restoring links between pay and pensions - it will now ballot its members for industrial action up to and including "all out strike."