Some facts draw your own conclusions...
The BACC know BA management well.
BA does not want strife with its current workforce.
BA wants the slots.
BA would if it could source pilots for those slots from the FPP
Reduced slots equals reduced number of pilots needed.
If BA allow a merge of seniority, it leaves them open for increased Ts and Cs above TUPE.
And finally,
The BA the BMICC will be consulting with are generally pilots of medium seniority about LH SFO on the MSL.