Hi @maddi. I went down a similar path to @Lisa1407. My tumours were found through Breastscreen which takes you down the Royal Melbourne Hospital path if you choose that option. I chose to use my private health insurance at RMH and also when doing chemo and radio at Peter Mac and had all the excesses and gaps paid for by the fund.
Along with @kmakm, I'm bamboozled by how it all works  :s .
I know too if you live more than 100km you'll be eligible for the Victorian Patient Transport Assistance scheme which subsidises travel and accommodation costs. Think Pink in St Kilda Rd also have a 2 bedroom apartment where you can stay whilst you're in Melbourne having treatment. The Cancer Council also helps with this.
Good luck going forward xox