That's exactly what FR will be saying. However, what will BA say when they get asked about the financial liklihood of them restarting LHR-DUB? If they make it clear that they're not likely to do this then that will blow this argument out of the water. Don't forget that EI are already pretty much an LCC on the DUB-LHR run and you can already only interline with a single through ticket.

Of course MOL may well decide to retain EI as a separate entity - if there's money for him in things like interlining through LHR then you can bet he'll keep it. Also, with a long haul operation to run and connecting passengers from the UK and elsewhere to recruit you may well see the ability to through-check baggage being made available even on certain FR flights.