It depends on a few things :
1. Who has the rights to show the commonwealth games in Aus. If it is a 576p "HD" broadcaster, then they are likely to originate in 576i. If it is a 1080i "HD" broadcaster then they may well shoot the ceremonies in HD.
2. Who would fund it? The Olympics in HD is funded mainly by NBC in the US and NHK in Japan. Neither of these countries are participants in the Commonwealth games - with Canada the only HD broadcasting nation apart from Aus.
I don't think they'd be prevented from doing so by anything other than economics and outlets. (In other words, they'd need the money to do it, and an HD outlet)
Don't forget - Aussie HD includes 576/50p as a broadcast format. As this isn't really a production format, you either shoot 1080/50i/1080/25p or 720/50p and downconvert, or 576/50i and de-interlace (albeit with a broadcast quality de-interlacer). The latter is much cheaper... Guess which is the common one for 576/50p broadcasters.
(Home and Away, whilst shot on 1080/25p cameras, is post-produced as 576/25psf in 576/50i SD DigiBeta edit suites, and then frame-doubled to 576/50p for TX. This is described as "HD" - but in reality it is only a little better than SD - the only difference being the lack of interlace pre-filtering vertically)