IRISH Rail is seeking 450 voluntary redundancies over the next four years.
The job losses, which the company says are aimed at tackling a deficit of €45.3m, represent almost 11pc of the company's workforce.
Staff are also facing cuts in sick leave entitlements, subsistence allowances and overtime, under a programme negotiated at the Labour Relations Commission.
"We have been engaged in a programme of cost reductions throughout the economic crisis," Irish Rail spokesman Barry Kenny said last night.
"We have reduced our annual costs by almost €70m since 2008 and over the past 10 years have been reducing staff numbers, which were 6,200 in 2002 and are now 4,100."
Staff have worked very successfully in helping to reduce costs, he said, and a voluntary severance package will be introduced on June 15.
Irish Rail had been to the Labour Relations Commission with the trade unions and a range of measures had been agreed. Unions will ballot on the proposals on June 20.
The company hoped to break even by 2015, he added.
Unions and management have agreed a package of further measures aimed at delivering another €12m in savings.
They include changes to pension arrangements, overtime, annual leave, uncertified sick leave and subsistence rates, reports said last night.
The company says the measures will deliver job security.
Last night, a spokesman for Transport Minister Leo Varadkar rejected suggestions that the timing of the severance package, on the eve of a bank holiday weekend, was deliberate. Nor was any directive given to Irish Rail, Bus Eireann or Bus Atha Cliath to defer decisions owing to the referendum.
On Wednesday, the Minister rejected suggestions by United Left Alliance TD Joan Collins that meetings to be held about further rationalisation at Bus Eireann were put off until after the referendum.