I thought the Irish registration on "off shore" fleets is more to do with lease conditions and tax implications, along with a simplified legal wrangling in case of un-scheduled lease return. Common practice and Ireland is not alone, Aeroflot for example have all the A320 fleet on the Bermudan (VP-B**)
The Alitalia Express aircraft on the Irish Reg are all owned by GECAS, Ireland. The majority of the leased aircraft into Alitalia are also Irish registered. Could be wrong but the flag of convenience is for legal and tax reasons only and does not effect the maintenance and operation of the airline. An Irish AOC though is a different matter.