PV,
There is no legal CASA reason why you can't use you own aircraft for any training -- provided you have a "legal" aircraft.
This is an excuse for you to shell big $$$ on hiring the school aircraft ---- "insurance", "OH&S" and other imaginative excuses are also heard, but the bottom line is always the same, pay 'm more money.
Look around for another source to do the training.
Tootle pip!!