Vodafone have added BYO option to their NBN plans. Critical Information Summary
Same as the post here but no more modem contract
https://www.ozbargain.com.au/node/451736
The conditions of the BYO plans appear to be the same.
I couldn’t find any options to sign up online so I signed up by chat.
One thing missing will be the 4G backup option. Not sure if you can utilise that option in BYO if you have a Vodafone Wi-Fi hub from somewhere else.
It might be that OP's network is a former optus cable area that is now HFC? Maybe?