This might be the case in VIC but I am not so confident about NSW. In NSW it is not a replica firearm but an imitation firearm. Quoting the relevant Act:
(2) For the purposes of the application (as provided by this section) of this Act to imitation firearms:
(a) an imitation firearm that is an imitation of a pistol is taken to be a pistol, and
(b) an imitation firearm that is an imitation of a prohibited firearm is taken to be a prohibited firearm.
(3) In this section, imitation firearm means an object that, regardless of its colour, weight or composition or the presence or absence of any moveable parts, substantially duplicates in appearance a firearm but that is not a firearm.
It will be interesting to see how this is ultimately classified.