The union claims the company is planning to turn Expressway services into a "low wage bus service"
Members of the National Bus and Rail Union (NBRU) at Bus Éireann are to be balloted on industrial action.
The union says the ballot is in response to company plans to turn Expressway services into a "low wage bus service".
The company and union attended talks at the Workplace Relations Commission today.
Speaking about today's talks, NBRU General Secretary Dermot O'Leary said: "The Company not alone indicated that it would not be in a position to contemplate any pay rises but also dropped an Industrial Relations bombshell in relation to the future of the Expressway service, threatening the livelihoods of 800 Bus Éireann workers.
"The NBRU will not tolerate the imposition of a Low Wage Bus Transport Service as a solution to a problem which has directly resulted from Department Policy," he added.
It comes amid growing unrest in public transport, with another 15 more days of Dublin Bus strikes due to take place this month and next.