The only way you could manage is have a lot more people living there which considering the climate is pretty hard to imagine.
There are the mines which are the reasons the NT has one of the highest per capita incomes in the world but not only was very little of the exploration done by the 30's the logistics meant that it was impractical at that time. The best bet to keep Centralia is to have an early Pacific War leading to an infrastructure build up similar to OTL and thus more settlement. The other option is to have Centralia as an Aboriginal Reserve. While Australia's attitudes at this time where hardly enlightened I suppose its possible that you could get a movement to "give 'em some desert so the outta our way".
There are the mines which are the reasons the NT has one of the highest per capita incomes in the world but not only was very little of the exploration done by the 30's the logistics meant that it was impractical at that time. The best bet to keep Centralia is to have an early Pacific War leading to an infrastructure build up similar to OTL and thus more settlement. The other option is to have Centralia as an Aboriginal Reserve. While Australia's attitudes at this time where hardly enlightened I suppose its possible that you could get a movement to "give 'em some desert so the outta our way".
I really don't think your going to come up with a plausible reason to have a couple of hundred thousand people decide they really want to live in a desert with minimal economic opportunities.
But rail extended to Alice Springs. That's within your CA, no?The one thing Australia has in abundance is empty space for secret military facilities the problem is logistics. Which is easier build your super secret base in the middle of the desert hundreds of miles from anywhere but near a railway and only 10 hours from a major urban centre to provide support or in the middle of nowhere with appalling transport links and days away from anywhere (remember I'm talking about the 20's not today). Adelaide is the centre of Australia's defense industry and thus over the years there have been a lot of secret projects in northern SA and I'm sure there still are. Going the extra 1000 miles provides zero extra security for considerable extra cost.