Update 8pm: Irish Rail management say they will not be affected by tomorrow's Bus Eireann strike.
However unions say they cannot rule out the possibility of the action spreading to other CIE services.
There are seven depots with shared services – which means some staff would have to cross a picket to go to work.
The NBRU's Dermot O'Leary says it is also possible that Dublin Bus and Irish Rail workers might strike in sympathy with their colleagues, even though they're not mandated to do so.
Update 5.30pm Minister Shane Ross has released a statement regarding the unions intentions to go on strike from midnight.
"I am deeply concerned at the impact that this strike will have on the travelling public.
In the last week, both management and trade unions have highlighted their willingness to discuss improvements in the company’s operations and efficiency.
It is now time for both sides to show this willingness can result in an acceptable and fair agreement that safeguards the company’s future and all of those who rely upon it."
Update 5.10pm Bus Éireann has said it is extremely disappointed at the announcement of strike action.
In a statement it said it will cause major inconvenience to our customers and exacerbate the perilous financial situation at the company.
It says losses for January and February are 41% higher than the same period last year.
It also claims that unions were only offering to give up €500,000 on a current overtime bill of €13m.
Update 3.10pm An all out strike has been declared at Bus Éireann, beginning at midnight.
General Secretary Dermot O’Leary said: “The letter issued on the 22 March by Bus Éireann Management is clearly the straw that has broken the back in terms of spelling out exactly what the real agenda is here, the new management structure at Bus Éireann have clearly signalled that they are intent on pursuing a race to the bottom in relation to workers jobs, terms and conditions and to reposition Bus Éireann as a low cost transport provider.
“It is a source of considerable regret that the travelling public are going to be discommoded as a result of the decision that the Trade Unions have been forced to take.”
SIPTU Sector Organiser, Willie Noone, said: “That our members have been forced to take this action is regrettable but it is necessary in order to protect public transport services into the future.”
Earlier: Bus Éireann union reps will meet today as an all-out strike looks set to go ahead next week.
Commuters face widespread disruption from Monday after bosses at the company said there was "no basis" for more talks.
Siptu representatives will meet with the other trade unions involved in the Bus Éireann dispute today to establish a common strategy and response to a management strategy of changes to conditions of employment at the company.
Siptu sector organiser Willie Noone said: "The correspondence from management, which was sent to our members, clearly targets certain categories of staff for cuts.
"This is being done while senior management, who played a huge role in creating the company’s current financial predicament, remain immune to making any contribution."
In a letter to staff yesterday, Bus Éireann management said it is "deeply disappointing" that it could not reach agreement with unions and "difficult decisions must subsequently be taken to safeguard our Company’s future".
Last night, the NBRU wrote to Ray Hernan, the acting CEO of Bus Eireann, stating that the ’accusation’ by Bus Éireann that there was a "refusal at the WRC to accept any reductions of earnings, including unnecessary overtime earnings" was untrue.