Only when a foreign country that we operated into requires it. The Capital ‘O’ legal opinion I’ve read (note for the knockers, not my opinion but one from an actual lawyer experienced in workplace law) is that this makes that particular vaccine an inherent requirement of the job.
The little ‘o’ opinion proffered at the same time was whether Aussie states or the Federation can introduce such a mandate for Australian citizens within Australia. There was a feeling offered in the opinion I read that this was an untested part of Aussie law.
So, yes, long haul crew can be required to have the jab if it’s a requirement to enter another country. Domestic is still a bit of a question mark.