You will recall that after BA set up Openskies, they purchased L'Avion, and the French AOC was thereafter maintained. Having set Openskies up as a known quantity, many of the original retired ex-BA trainers and crew left, and with L'Avion crew and a different AOC, more than half of what now remains is probably not what BA mainline would describe as a known quantity.
The bmi AOC is not going to be estinguished overnight (regardless of type, the crews are not trained on BA procedures), and neither will any integration be overnight. bmi will exist for a while even if the aircraft are rapidly repainted.
Also, a plc can remain if the debt is listed (which it is at BA) - it affects the disclosure / reporting requirements