It's very simple. BASSA have to give a week's notice of any strike. BA can simply roster non-striking cabin crew for those days and not roster those people they know are likely to strike. If the strike is cancelled, they will still have adequate cover, and the would-be strikers will still lose out on the allowances they could have earned.
They will fly 100% of LH services, strikers will lose yet more money, and eventually the will to keep missing out on both your salary and lucrative LH trips will reduce the number of strikers until Bedfont is Holley and the few remaining idiots that believe in him and MAYBE some of his BASSA rep cronies (many of whom will be off sick or flying because they don't want to lose their staff travel, oh no!).