Metro man, my apologies. There doesn't seem to be a section in the Regs that covers this scenario
. This
could mean that the creator of the Regulations hadn't struck this before.
Immigration Dob-In Line
The above link is for Immigration's compliance people. If the issue's bugging you, they're probably worth a call, either for the correct answer (if it's legit) or to investigate (if it isn't). It probably depends on what Australian visas these crew hold, if any. If they do hold 457s sponsored by Jetstar, there is no reason why they can't work. The question would be how Jetstar was able to sponsor them when there are plenty of suitable applicants in Australia.