I'm from Victoria. In Vic, we have what looks like the same situation in NSW - you need 2 statutory declarations from medical practitioners to vertify that you've had "sex affirmation surgery'.
A few years ago when I had chest surgery, I asked the surgeon if he would sign the form to get the sex changed on my birth certificate but he said no. He apologised and said that it wasn't worth losing his registration over :(
Someone from Vic once did tell me that they knew a transguy (in Vic) who had managed to get the sex on their birth certificate changed without having a hysto but they didn't say how.
Sorry I can't help more but maybe you could ask the Gender Centre in Sydney? http://www.gendercentre.org.au/