I strongly suspect that in Oz, if you tried that someone would put you in gaol.
There are very strict rules about process and product ingredients and not mixing them when working with food. If you go to McDonalds, the paper placemat on your tray is there because the tray is/may be made from recycled plastic, food cant come into contact with recycled plastic.
In a brewery I wouldn't even think about it, legality aside, potable water is cheap, the risks of the public reaction to your beer having a perceived "piss" content could be very negative. That aside you would need a very good (expensive) analysis on a batch by batch basis, just for the mineral content.
Its great to think that the discharge from a tertiary sewage treatment plant is good enough to drink (better than blind mullets off Bondi beach as was the case only a couple of decades ago), but I wouldn't even think of brewing with it on a commercial bases.
Mark