This pension scheme was created before the privatisation of Aer Lingus and involved them, the DAA, and SR Technics. SR Technics shut down their Dublin operation and walked away from their pension commitments, and they're still a profitable company operating in Ireland. So why should Aer Lingus have to cover the pension shortfall left by SRT and essentially pay for the pensions of DAA employees who have better pension entitlements than new Aer Lingus employees? (At least that's my understanding of it)
Hopefully for everyone involved it will mean the splitting up of the pension scheme, a crazy one to have initiated.