Actually discovered this with my Android which has a Rogers Pay As You Go SIM at the moment.
I must have tried to access something before it had finished connecting to my Wi-Fi access point. I received an SMS from 3330 stating:
The URL is only accessible from a smart phone on the Rogers network, with Wi-Fi disabled. The gist of it is you can now buy a Data Day Pass for $2.99. Good for the day or 20MB, but if you use up the 20MB you can buy another pass for $2.99. $0.03/kB while roaming. Tethering is specifically excluded.
This doesn't get you Blackberry Data, but may be of some use to people running without data plans. Seems to be handy on my Android