CIÉ's two pension schemes had a total deficit of €459m at the end of 2016 when risk reserves are factored in, the Oireachtas Committee on Transport, Tourism and Sport has heard.
CIÉ owns Dublin Bus, Bus Éireann and Iarnród Éireann and has two pension schemes on which 16,700 employees, former workers and retirees depend.
The regular wage scheme, which covers 75% of staff members, accounts for €98m of that total deficit including risk reserves.
However, the CIÉ superannuation scheme, which only covers a quarter of the workforce, has a total deficit of €361m, also including risk reserves.
A ten-year reform programme was established in 2013 to restore the schemes to solvency, but so far targets have not been met, so a revised funding proposal will have to be submitted to the Pensions Authority to explain how solvency will be restored.
CIÉ blames three factors for the deficits: falling long-term interest rates, increased longevity, and increasing regulation to reduce risk and protect pension benefits.
The company stresses that it is not seeking to implement pension reforms to cut costs, but rather to improve the security of members' benefits.
It added that it has fully complied with the rules of the pension schemes.
The measures CIÉ is proposing for the bigger regular wage scheme include raising the retirement age and capping pensionable pay at current pay or 3.3 times state benefit, whichever is greater.
Changes to the superannuation scheme, which carried €361m of the deficit, include raising the retirement age, closing the scheme to new entrants, and introducing a "best in class" scheme for additional voluntary contributions.
However, CIÉ says there has been no substantive engagement yet on measures to address the risk to members’ benefits in the superannuation scheme.
It notes that it has fully engaged with unions with the help of the Workplace Relations Commission but says this process is "in abeyance".
The company stressed that the current difficulties for the schemes were not triggered by the 1994 consolidation of pension schemes in agreement with staff.
It also said it was not appropriate for CIÉ to engage on matters that were exclusively the responsibility of the pension committee.
The National Bus and Rail Union has told the Oireachtas committee that its bottom line is that it must secure a solution where the pension benefits and entitlements which CIÉ pension scheme members had paid for would be honoured in full.
General Secretary of NBRU Dermot O'Leary was addressing the committee on the deficits in the company's two pension schemes totalling €459m (when risk reserves are factored in).
He reiterated a call for a stakeholder forum chaired by an agreed independent party to resolve the row.
He also argued that the pensions row dated back to 2009, when the two schemes between them had a total deficit of €500m.
The NBRU insists that if CIÉ had followed advice as far back as 2009 and raised its contributions to the schemes, the deficit in both schemes might now be significantly lower.
There is also a difference of interpretation between management and unions on the obligations set out in a statutory instrument of 2000.
Mr O'Leary said the CIÉ board should maintain the solvency of the schemes.
He also pointed to the difficulty facing 900 members who paid a D1 social insurance contribution and thus do not qualify for most State benefits, including the State old-age pension, and are thus totally reliant on the CIÉ pension schemes.
SIPTU Divisional Organiser Greg Ennis cited what he described as an "explosive" and "damning" internal CIÉ document from 2009, which queried whether the company's pensions strategy would stand up in a court of law.
He also told the Oireachtas Committee it may owe hundreds of millions of euro in unpaid contributions to the company's two pension schemes.
The 2009 CIÉ document states that at the time, most CIÉ employees realised that their schemes' funds had not been immune from the downturn.
However, it went on to say that many CIÉ employees also realised that a previous 1994 pension restructuring had benefited CIÉ more than the scheme members.
It said that members were aware of commitments given by CIÉ in 1994 in relation to funding and other matters, but would see the present "predicament" in which the schemes found themselves as the time for CIÉ to "deliver".
The document says it can be expected at the very least that there will be some form of industrial action but goes on to warn: "However, the bigger problem may come from a referral of the issues to the Law Courts. If that is done the rule covering the Board's contributions will be examined".
"In addition, the Board's intentions and commitments given will emerge as part of Discovery. The Minister of the day signed the Order giving effect to the terms of the Statutory Instruments (SIs). The Department of Transport and the Department of Finance were fully aware of the terms of the SIs including the mechanism triggering a review of contributions".