The IAA have the radar, the personnel, the communications and the capacity.
Actually so do ScACC. The service is to be done with both Scottish and Irish radars. ScACC could easily do the service and I believe proposed doing so many years ago.
I have also heard the story that there will be no charges for the first 2 years so that does look like somebody is subsidising it initially.
No comparison with the London airspace transfer. The overall efficiency of that airspace was much improved (delays down about 95%) by the move of sectors which London could not staff. The NOTA will end up costing lots of airlines money who never go near the North Atlantic.