The stated need is to replace the PC-9Ms in the CAS (COIN?) role with a possible intercept capability added on. A Bear or Backfire isn't going to materialise near / in Irish airspace without having been followed for a long time, I would have thought the same would apply to a hijacked civilian aircraft - it is in everyone's interest to pass the information on to those who can act on it. We aren't talking about finding an LO threat. If the Irish government goes down this road, aren't they likely to the throw the money at a ground radar capable of being used for GCI to visual range using a fairly basic (no AI radar) aircraft capable of carrying short range AAMs and a cannon (with hardpoints for mudmoving ordnance)? Sounds a bit like a modern version of the Hawk T1A "experiment" (without F-4s or F.3s to lead them
) or a Hawk 200 successor if you did want AI radar. I am aware a certain TD reacted strongly to RAF QRA aircraft operating in Irish airspace - allegedly without first informing the Irish (ATC?) authorities so Typhoons handing over to a less capable aircraft and shadowing from outside Irish airspace would perhaps have political mileage.
However, Declan275 has probably hit the nail on the head.