EI flights are now showing between London and Dublin on ba.com as BA codeshares.
Avios earning appears to be at BA rates, rather than at EI rates, assuming you will earn at the way my dummy booking said.
The prices are *not* the same as the Aer Lingus website, and may be higher or lower for given flights. All flights in my sampling all seem to include 1 piece of hand luggage, and so are comparable to Plus fares, I guess, although it doesn't say anything about seat selection.