I'm not saying there is any real evidence for something like this to happen, just that the opportunity is there, and I wouldn't put it past a business to leverage a position like that.
Of course, it gets trickier when the same company provides capped Internet access and uncapped non-IP-based services.
FYI, you can see their exorbitantly priced plans here: http://my.bigpond.com/internetplans/broadband/adsl/plansando... Their overage charges are $1500 AUD per 10GB. Many A Current Afair story have been about some poor family slugged with a $10,000+ internet bill.
Since Usage Allowance's are so low in Australia, pretty much all ISP's provide unmetered value added benefits, like ftp mirrors and game servers. I had never realised that these kinds of thing were not net neutral. If these features were revoked, my internet bills would increase by 25%, which I obviously would not be too pleased about. Gah, now I am troubled; I'll be thinking about this all day.
EDIT: It appears these kinds of things are net neutral, because they don't restrict other people's packets.