Just conjecture, but maybe Unite have refused to bankroll BASSA's strike costs/punitive costs to be paid to BA and BASSA have threatened to leave Unite if they don't have their support.
Neither Unite nor BASSA can afford to lose (financially) so they have come up with a compromise whereby a QC is engaged (and paid for by Unite), the result of which will determine whether Unite are prepared to gamble the union for BASSA.
It will therefore be interesting to see what the QC says.
In the meantime BA will have imposed the changes and crews will have operated at the reduced levels, even if the QC backs BASSA and a strike ballot is held, and all the VR's will have left and part time contracts be in place.
If BASSA then get a strike mandate, BA will let it go ahead and people who don't turn up to work will be deemed as having resigned and the only way back will be onto New Fleet.
Result: game set and match to BA.
Note: this is not meant to more than indicate a possible scenario to BA Cabin Crew. I wish them no harm or financial penalty, but merely to point out how they are being let down by their elected reps.