Optus did (does?) something similar
Optus had (has?) a home gateway device that would allow your Optus Mobile to connect to a local picocell in your house to give you better mobile coverage if you were in a blackspot. Of course, that picocell then used your Optus internet connection, and your data allowance, to provide that service. On top of that the pico cell *still* needed to be able to pick up a (weak) signal from a proper mobile base station to authenticate the mobile service. So you got to pay extra for the picocell, pay for the internet connection and data, and pay for the mobile service that was connecting to it. TRIPLE PLAY!
So kinda the same thing I guess... why should the carriers bother building their own network when they can double bill the users to provide the service for them?
(Why is there no $$ signs icon?)
I also seem to recall there was something in the Australian Telecomunications act that prevented "non Carriers" from offering a service that allowed them to connect to the internet. It was something that caused a headache for the "Sydney Wi-Fi" open-mesh network that started many years ago. If so, then perhaps it is still OK for Telstra to charge for access "over their equipment", but the user can't earn anything from it without breaching the act... or some such loophole I'm sure Telstra would use to explain the rort.