maggot,
What's in it for the company to create positions in Perth and then base balance to the East Coast? Why wouldn't they just make the positions on the East Coast to begin with?
My personal belief is that the A330 will almost entirely disappear from East-West flying and be re-deployed internationally. Maybe one or two flights in the morning and afternoon peak each day will stay, but other than that it will be 737s, meaning plenty of flying ex Perth. Virgin are doing the same with their A330s once they start China and Abu Dhabi.
The rumours of more international flying ex Perth for the 737 was floating around a while back too, that could be the other reason.