I can't see how BASSA can recommend rejection of this offer. If they do, then their members will vote in line with their recommendation - although the majority won't be great. But what good would that do? Tony Woodley will refuse to sanction a strike ballot, so there will be no strike to pressure BA and things will remain as they are: no pay rise, no ST returned, no variable top up pay, no prospect of sacked people getting their jobs back.
You can now see why Willie Walsh has offered the return of ST after repeatedly saying that he would never do so. He has lost that battle but in doing so he will win the war.