I have certainly seen it written in some BAA document that Aer Lingus are not moving in the interim moves which start immediately after most BA flights move to T5. On the other hand there are plenty of press releases saying they WILL move to T3, albeit rather dated now.
Since Aer Lingus have pulled out of Oneworld they may no longer be welcome in T3 and neither will they be welcome in T1, the SA terminal.
It's going to make a mockery of code shares if they are not co-located with their partners.
International passengers making connections to UK and Ireland are going to have a fun time over the coming year!
