On the current schedule, it looks as though all four LHR-MME-LHR flights can be operated on the same aircraft:
BD330 departs LHR 06:30 (arrive MME 07:30)
BD331 arrives LHR 09:15 (depart MME 07:55)
BD332 departs LHR 09:50 (arrive MME 10:55)
BD333 arrives LHR 12:40 (depart MME 11:25)
BD338 departs LHR 17:00 (arrives MME 18:05)
BD339 arrives LHR 19:45 (departs MME 18:40)
BD340 departs LHR 20:25 (arrives MME 21:25)
BD345 arrives LHR 22:55 (departs MME 21:50)
I may be missing something, but this must be operated by the same aircraft - an Embraer. It would be illogical to fly an Embraer up on the BD330, park it in MME all day and then operate back on BD345, then using an Airbus to operate the 331/332/333/338/339/340.
So yes, same as LHR-ABZ and LHR-HAJ, it looks as though the MME route will be an all-Embraer operation for this summer.