presumably having to withdraw from the EI codeshare to / from Belfast and Dublin
jdcg; this is the most absurd presumption. BA are very happy with the level of feed from EI via LHR from DUB, ORK, SNN and BFS, why on earth would they want to withdraw from the codeshare with EI. Even if they do choose to operate on DUB & BHD to LHR?
They cooperated when they were on DUB LHR and they still cooperate today. If BA do opt to fly to Dublin or Belfast City post bmi, they still will probably have 4 or at most 5 rotations a day and EI in the case of DUB will have a lot more, hence potential to feed BA LHR network.
BA have axed LHRDUB in March 1991, and then in recent years axed LGWDUB and LCYDUB was abandoned mid season as it was a disaster. I cant see them touching DUB.