I believe Unite, the parent union of BASSA, have stated on their website that the union will cover all court costs of the plaintives.
Anyone with access to the BASSA site may be able to confirm this.
If I was on the list, I would also want binding guarantees that I would also be indemnified for any compensation awarded by the court to BA.
Not only should anyone thinking of joining the case as a claimant insist on written indemnity for court costs from BASSA and Unite, I would insist on seeing at some of the legal advice received by BASSA and Unite on the merits of the case before signing up.
You have to go into this with your eyes wide open knowing exactly what you're letting yourself in for.