With so many flights from LHR to DUB (including Aer Lingus) there isn't any point to worrying about this. If you are in danger of missing conformance you will get rebooked anyway to the next available flight. But to answer part of the question, BA takes ownership 24 hours before departure (presumably somewhere on the AA network) until arrival into DUB, so BA would only touch the ticket at that point. This counts as a complex ticket so it's best to react to events rather than being proactive based on possible events.