Looks good. Alice Springs has plenty of resources. Unfortunately, also lots of people, many of them transients, because it's a hub of tourism, as well as being an air hub for a lot of people travelling out to remote sites to work, though once cleansed it shouldn't be all that hard to hold, or to defend. I'm wondering how climate features, like the periodic flooding of the Todd River, would affect things - would it sweep the grosslings away from the walls, or bring in a mass of ravening camel and buffalo beasts from further north? And again, marsupials - any settlements out there would be in huge strife if marsupials beastify. Sure, the big ones like kangaroos would be a hazard, but in the long term I think the little ones would be a much greater danger. Consider that for every kangaroo there are thousands, probably tens of thousands, of the little guys - desert mice, hopping mice, dunnarts, marsupial rats and all that lot. Echidnas. Quokkas. Quolls. Tasmanian Devils. Wombats. And, gods help us, the Antechinus. Those things are tiny, yeah, but they already behave like a shrew on speed, and if they beastified, or fused - would be nasty.
If I were setting up such a refuge, I might raid Alice Springs, but would be more likely to do fortified permanent bases at Kata Tjuta, Mintabie, Woomera (the old Rocket Range), Pimba (Spud Murphy's Roadhouse would make a pretty good base), Copper Hills, maybe Uluru or Coober Pedy if there weren't too many tourists there when things fell apart. But my first choice would have to be Giles. In part because the climate is extreme, in part because, being as it is the most isolated settlement in Australia, most people either don't even know it's there, wouldn't think to go there, or are likely to die on the way there. Last time I was there, on my way out to Lake Christopher and the Tanami Desert, the population was 5, I think now it has dropped to 3. But my main reasons for Giles are that if you know what to look for that land is rich - the Warlpiri did pretty well there for thousands of years; and that inland, north of Giles, is a lot of really broken country, within the curve of the Schwerin Mural Crescent, much of it still only superficially explored, or not explored at all. Very few people, and you only have to walk on that land to feel how alive it is. If magic came back anywhere, it would be there. South of there are the Mirning/Myrning people, down where the Nullarbor meets the sea, and they are folk who still have a very active tradition.