Its not over till the fat lady sings with the bmi lhr dub route just yet.
Define "just yet". 28th October? One of the scenarios I outlined will play out. IAG will not run their own operation and a codeshare on the same route. If they pull the codeshare out of Dublin, it would would EI want to continue it from Shannon /Cork? Maybe, maybe not - but it would be messy.
IAG, in the form of BA, make it quite clear on their views of the relative value of domestic / short haul in LHR when there is any disruption at LHR - they cancel. For the traveller, the retention of the codeshare over IAG operation could actually be beneficial in those situations, as EI would try to fly something whereas BA would just blanket cancel. Whether this is worth the price increase EI would inevitably get away with on LHR routes is for the individual to decide when booking as against transfer via CDG, FRA or AMS.
MD