Channel 10 have the broadcast rights for the games, and the only coverage the ABC would have would be news items. I have not heard any comment about the ABC only showing Aussie gold medal ceremonies. The commercial channels have been televising major sporting events for years, simply because the ABC can not match the obscene amounts of money the commercials seem to be able to afford. I suppose that's because the advertising revenue generated by such events is so high, and we, the viewing public, have to endure endless TV ads if we want to watch.
I am old enough to remember the "good old days", when the ad-free ABC used to televise test match Rugby and cricket, as well as the Olympic and Commonwealth Games. What Australian of a certain age will ever forget commentator Norman "Nugget" May's famous "GOLD, GOLD for Australia" call in the men's 4x100 Medley Relay final at the 1980 Moscow Olympics. The recording of that call has been added to National Film and Sound Archive's Sounds of Australia collection in Canberra.
Peter.