Answer:
Banyans are a fig. Australia has many native fig species, some of which grow in isolated pockets in arid areas of Australia. These include Ficus macrophylla, Ficus tinctoria, Ficus rubiginosa. I have seen Ficus brachypoda, Desert Fig growing on rock in Central Australia, but right next to small bodies of water such as permanent waterholes and deep wells. If they were able to colonise dune country and gibber desert they probably would have by now and they would be far better adapted than banyans.
I find it interesting that you have suggested banyans specifically when there is a host of other Australian native plants which thrive in arid country and create a self-sustaining ecosystem which supports food plants and a great diversity of animals.
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