One of your 'mates' who sits at the front - working it out - is he a specialist in Industrial Relations now? Oh yes I forgot - once you learned how to fly an airplane - you automatically know everything else in the world don't you?
One or two have LLBs. Some others even know how to read and use Google.
Further, BA will only have mentioned a potential illegality with the ballot if there actually is one. They would have nothing to gain otherwise.
So Lurker, in your humble opinion, is the ballot legal?
"Yes" or
"No" will do. Anything else is irrelevant.