NIR and IE went halves on the Enterprise - which is a problem because there are Mk3s which could be directed onto Enterprise but it would require NIR to put up some money.
The real problem is that the Dublin-Dundalk line needs a quantum increase in commuter capacity while respecting terminus slot capacity (*cough* bilevels *cough*
) but instead commuters have to crowd into Intercity services because going from 4 to 6 to 8 DMUs is not staying sufficiently ahead of demand growth.