Can't speak for Australia, but certainly a common route in the UK. In fact, one of the drivers behind the current N. Sea salaries was a desire to stem the flow a few years ago.
Case in point (which I'm sure he won't mind me saying): ThridleOpDes, one of the regulars here, BHL B212 and AS332, went straight to BMI on Airbus 320, and is now an A340 Capt in the ME. Plenty more similar examples (ex Chief Training Captain easyjet is also ex BHL, etc etc)
Mind you, plenty come back too!