Monger,
Remember any union is only as strong as its' members. Last year both PCS and the engineers voted to accept the original offer but the ATCOs rejected. What were the executive expected to do-completely ignore the members??
Maybe you are right that there should be a single union for all ATC staff but as technology threatens jobs in the future is this really feasible?
I don't think Prospect cares less about the engineers but is duty bound to take account of what the ATCO membership indicate at the annual conference.