TBH, Australia is a bit of a mess, we used to use AS923, but we now use AU915, a lot of gateways are older (AS923), and some are newer (AU915), however AU915 is allowed to use more power, and AS923 is weaker.

As for my experience, I had to buy a gateway for my house, but a train station near my workplace already had a gateway professionally setup, and my university has a gateway too. So anywhere I'd usually take my backpack has coverage.

You can use a service called TTN Mapper to see the gateways near you with a heatmap to show their coverage.

I've also just left a comment on the Traccar forums with some useful info regarding the T1000.