Keep in mind that even if this rock is super fresh straight from Australia, there will still be some die off of the stuff on the rock. The rock is flown on an airplane in a box without water. So, even though most of it will still be very alive, you will get some die off, especially the coralline algae. All the beneficial bacteria and such will eventually come back and flourish, but you can't expect rock like this to have zero die off after such a trip.
If you add it to an established tank, it will cause at least a slight cycle with maybe some diatom blooms, etc. The degree to which this occurs will depend on how long the rock was out of the water after leaving the reef where it's harvested.
I've bought Aussie rock several times now and it generally looks amazing when you first open the box, but within a couple of weeks it's pure white in the tank. It can take months for the original colors to come back, but they do eventually come back. It's beautiful rock though.