Na it's generally just open to the public, think Souths have one pre-season there a year "Return to Redfern", pretty sure they train there too, top right hand side still has their crest, but the rest of the year they play at the ANZ which is a soul destroying stadium both in location and attendance to capacity ratio.
Wests do as well for some odd reason, it's basically in Parramatta. I guess the suburban grounds don't bring in the dollar but for me the best place to play NRL games out of the suburban grounds is at the Allianz...only problem being there's no public transport other than a bus and what will be the light rail in a few years and the Allianz already has three tenants in Roosters, Sydney FC and the Warritahs. Ironically the best supported of the three are Sydney FC.
Theres lightyears difference between AFL and NRL at the moment, Sydneys over crowded but personally I just don't think the funding is in it for them to stay at their home grounds so the NRL want government funding to turn the ANZ into a primary NRL stadium and the government want to split resources between the ANZ and the Allianz. However less entertaining AFL maybe, the MCG and Etihad are positioned perfectly and they get the crowds.