If I read this correctly if your residence is currently Australia and that is your domicile then you can hold a American CDL without surrendering your Australian License.
It's hard for me to stay that you cannot hold more than ONE license anywhere in these United States when these executions keep coming up.
I leave it to you and whatever American State you are currently in that issued you the CDL to have the knowledge necessary to keep you legal.
If I ever get to Australia it will be a life time dream to have a hold of one of your half million pound 4 trailer road train for a hour or so. I don't know if there is a ranch or something down there with private land big enough for that because they wont do that on my basic American Car license.
Perhaps the reason we were allowed to keep ours was cause we were on Visas which meant we were not staying in the USA permanently or quite simply some Dept Transport offices don't know all the rules either way no one asked us to surrender our aussie licenses. Its like if i became a US citizen would i have to surrender my Aussie passport? the answer is no as you can hold duel citizen ship so when i go back to Oz i'd use my aussie passport when i return to the USA i'd use my American passport. If you want to drive Road trains yes there's plenty of room the majority of road trains are actually small only 2 full size trailers or an A- B set up which is a full 45' + a 1/2 22' + a full 45' around 70 tonne all up so one don't want to encounter many hills. Out the NT or WA they may run 3 - 4 full size 45' footers. close to 100 metric tonne