At best you get two chunks, Dublin and rest
Privatisation is no different to current really, as its all a contract.
Difference is there is no motivation for Irish Rail to get better, no risk. In a private sector approach, you can't make money unless you deliver.
The complete opposite to Southern is Chiltern
https://en.wikipedia.org/wiki/Chiltern_Railways and this is far closer to Irish Rail's operating conditions and asset quality and conditions