If you look at the relevant ADRs (ADR 14 02) you will find that mirrors can be replaced with rear view cameras but must give the same coverage as required of the mirrors you are replacing. For example if you replace a side towing mirror the camera would need to mounted far enough out so that it can see down the side or the van.
strangly enough a few months ago I emailed the RMS in NSW on this very subject and they advised me that the rear camera can only be used in reverse and not when moving forward very confusing advise here who the hell do you believe
If you ask about a reversing camera, then yes you can only us it while in reverse, but if you ask about the camera as a drivers aid, then it is legal to use all the time !!!! ?????
Is that guilding the lilly a little bit its just a play on words they are both doing the same thing and I did state a camera on the back when I enquired where do we find the information on a drivers aid and there is a problem with the driver being able to see the VDU while driving as well along with the fact of obscuring the windscreen area with the monitor