The timing is impeccable, since the iPhone 3G has launched and some Telcos aren't even trying to compete in the mobile data space.
The ACCC has sent letters asking all the Telcos to outline their strategies for educating users on the excess cost of mobile data on the networks. They've also cautioned users to pay particular attention to their contracts so that they can avoid a hefty charge come bill-time.
So, don't expect anything to change in the short term - this is more the ACCC sticking its head up and telling everyone that it's watching the situation, not an announcement for upcoming change. Which is a shame, really...