They use T2 but Aer Lingus said that they may need to operate some flights from Pier B in T1.
If the website says EI flights will arrive in T1. They will but passengers will not.
The aircraft will arrive on stand in T1 but passengers will do customs and claim baggage from T2. There is a walkway for arriving passenger at Pier B to get to T2 arrivals.
EI have a lot of flights arriving after midnight and stands are a problem.