I don't know how drastic the outcomes could be, but there seems to be a lot at stake here. If Qantas management win, it will surely have poignant results for other unions.
I think that they will think that it's worth fighting this one all the way. If the Unions lose this and then give up, they may have lost the battle, but they will have also the lost war. They will be in so much of a weaker negotiating position. At any moment knowing they could be trumped, it will be another example of breaking unions' backs. Any (un)qualified opinions on this?