"They aren't going to encourage people to go via DUB "
Why not?
More and more people are viewing EI/DUB as a good alternative to BA/LHR.
If they (IAG/BA) 'own' EI, and many people currently DO avoid LHR (for a number of good reasons) and they (BA/EI/IAG) could, probably would gain business via DUB , Transatlantic, which they would otherwise not get !
They , IAG/BA , would then gain add revenue/profit which otherwise would go to another carrier.e.g. AF/KL/LH etc.