Question - If crew turn up and operate on the 16th and thereafter, will they be deemed to have accepted the new crewing levels? I take it that anyone that refuses to operate will be suspended - how many will do that if there is no guarantee of support for a strike?
If, as BA says, these changes are non-contractual, then from a legal point of view there should be no need for crew to indicate their acceptance, whether by written agreement or conduct.
I don't think crew operating at the revised crewing levels would prejudice a strike ballot either. If this point was ever raised, the defence would be crew had to follow instructions to avoid discliplinary action.