The xONEx tickets list allowed carriers on them, and that stays valid for the duration of the ticket (including adding new segments on any of those carriers), so there is potentially 2 more years to fly EI.

The lounge access disappears when EI leaves OW, and of course the only J on EI is trans-Atlantic (so you would have to be flying EI in J to use the lounge in DUB). While the DUB lounge is pretty poor, the rest of the airport is even more dire (makes TBIT look lavish). I'm pretty sure that the only relationship EI will have with AA and BA will be for codeshares (BA has 0 flights LHR-DUB so really needs this codeshare; all the BA flights are LGW-DUB; AA seems to have started new service to Ireland so it is mostly EI wanting codeshares on AA feeder routes in the US).