Personally, I would think the NJS Cabin Crew are quite safe from the threat of Jetstar taking the contract.
Jetstar is short of crew all over the place, with training school after training school going through for each base that we currently have. We do not possess the ability to suddenly open up another base without sacrificing whatever business plans are in the pipeline for our own new routes and increased frequencies.
Furthermore, I strongly doubt that, with the exception of Perth, you'd find any current crew wishing to relocate to Alice Springs, for example.
If in fact NJS didn't secure the contract, I would naturally presume they'd be given the option to at least skip an interview stage for Jetstar (like they did in BNE not too long ago).
As GalleyHag says, get the FAAA onto it. That is if, of course, they're not already doing something about it (NJS is pretty close to their hearts, given all the recent goings on over there!).