It is entirely possible that BA continuing the action has a slightly different aim.
BASSA appear to be the stumbling block for both UNITE and BA, in their eyes at least. BA can only negotiate with UNITE but UNITE cannot be trusted to deliver a viable deal in the eys of BA.
BA could continue with the case and get approval to recover costs from UNITE. As BASSA is 'ringfenced' as a seperate company (or so I believe) then BA can seek redress and have the BASSA branch effectively put out of business without affecting UNITE. Existing union members are largely unaffected but can either join UNITE or PCCC.
UNITE can then negotiate for a peaceful solution and give all members a vote on what to do, after encouraging all those who may have left BASSA to rejoin UNITE and outvote the entrenched die-hards.
In theory at least - nobody gets sacked, and a compromise is reached. UNITE is then 'united' and in a better position to speak for the majority who do not wish to strike.
I am still flying BA on short haul and have thus far not seen any bad behaviour towards us SLF.