Anyone who thinks the A330 will be domestic only is deluding themselves.
Have a quick think about it. The 777 has shown itself to be too big for Virgin, whilst the 737 was never intended to be medium haul international product.
If Virgin is to move further into medium haul international (Asia) then it will need a mid sized widebody to do it.
Now, i guess it may not be the A330, and could be a 787 or A350, but my money is on the A330 heading up into S.E Asia in the near to mid term future.
I would suggest that those taking under the table deals to (secure?) their future on a widebody, should give a fair amount of thought to the implications of flying yet another Virgin aircraft on international sectors whilst being governed by a domestic EBA (or common law contract). Didn't work last time, probably won't work next time.
I would think the unions would be giving this subject more than just a little consideration.