AO,
I don't really wish to fully answer your question because I don't have the time right now.Maybe someone else here will.
Suffice to say that a union may ballot for Industrial Action for one issue only.In this case they made it pay because in 8 months the negotiations have gone nowhere.
Believe me, if all was sweetness and light at VS the turnout /votes for,would not have been nearly so great.
It is this level of discontent which has been brewing for some years which has finally spilled out.
The company carried out a staff survey last autumn and the flight ops management are reported to have achieved a 6% approval rating.
6%