There's no difference in charges between T1 and T2, so there's no reason why Aer Lingus would switch from T2 to T1.
This is bizarre. Why not? If airbridges etc have a commercial value to the airlines (which I don't necessarily believe, but some seem to think so); if T1 is so bad and unliked by costomers and T2 is better and more attractive to them; if the debt on T2 needs repaying; then DAA should be charging more for their use.
Not doing so implies that the low cost users are subsidizing the higher value travellers. It also implies that the airlines are not actually that impressed with the facilities on offer in T2 over those in T1, and higher charges would have meant the white elelphant would have been an even bigger white elephant as airlines stayed put.
MD