I would say that the current EBA prohibts
VB from using other entities. In the current document "5.b - applies to all cabin crew operating on Virgin Blue aircraft."
Over the years QF have probably had agreements amended slightly to include the recruitment of part timers and casuals which would erode conditions for all. The latest LH agreement allowing the hiring of QCCA whilst giving short term pay increases for part a employees will eventually lead to many more QCCA or part b employees being hired by QF and thus the cheaper workforce will have taken over the more expensive workforce and will vote in anything that gives them a better deal at the expense of the senior crew.
I think that we are better off sticking with just two pay levels, no casuals, a few more part time positions especially for those coming back from mat leave and exclusivity on the operation of the
VB fleet. The more pay levels there are the less likely you will be called out as senior crew. The new ones will get called out all the time saving the company money whilst the senior crew get stuck with short day trips or whatever works out to be cheapest.
You may think that you are only going to be here for another six months but most of you will still be flying in 10 years time. Think about that when you sign off on a new EBA.