As much as I like taking the Shinkansen when in Japan, count me as skeptical about the prospects of a successful very fast train that runs any distance in Australia. But if we have to build one, instead of doing all this tunnelling (I heard someone on the radio saying that the Melbourne to Sydney one requires sixty something kilometres of tunnels) I'd like to see this design:
How cool was that? Avoids the 'roo on the track issue, too (unless you catch a very unlucky one mid-bound.) And instead of having just one leave the station every 2 hours or so, you could have one small one leave every ten minutes. Sort of like Musk's Hyperloop, without the claustrophobia.
Clearly, this desire to try for something like a Shinkansen in Australia will not go away from the public's mind. But like some itches that need to be scratched, it's probably best to try small scale before committing to large. Buy just a couple of handweights before putting that home gym machine on the credit card; or a set of rubber cuffs before the deluxe ceiling swing. (I have no idea what I am talking about in either case.)
So, just build the thing for a relatively short, relatively useful distance, like Sydney to Canberra, and see how that goes before spending money on expanding it beyond that. In fact, given how long both projects will seemingly take, build it from the new airport site at Badgerys Creek to Canberra, maybe? Put a relatively fast train from Central to Badgerys, perhaps - with an automatic luggage transfer to the really fast train? (I am assuming that might cut costs a fair bit.)
You can thank me later, Australia, for my useful suggestions....