Jim,
To answer your key question: “Are there some particular towns that are well-removed from the major population centers on the east coast –perhaps up in The Wet– that would be well-suited as safe havens?” You would need to define what constituted a major population center.
There are five cities/regions with a population over a million [people]: Sydney (due to their close proximity to Sydney I would include the cities of Newcastle [pop 510,000] and Wollongong [pop 275,000] as part of Sydney), Melbourne (including the city of Geelong [pop 165,000]), Brisbane (including the Gold Coast/Tweed region [pop 485,000], the Sunshine Coast region [pop 215,000], and Toowoomba [120,000]), Adelaide, and Perth.
Once you put these aside we are left with the following cities with a population of greater than 100,000:
Canberra [pop 325,000]
Hobart [pop 203,000]
Townsville [pop 150,000]
Cairns [pop 125,000]
Darwin [pop 111,000]
Launceston [pop 105,000]
Albury-Wodonga [pop 100,000]
Of these Canberra and Albury-Wodonga are out as they are within 300 miles of Sydney and Melbourne as well as on the main line of likely advance for the respective Golden Hordes.
Launceston and Hobart are on the island of Tasmania.
Townsville is home to 3 Brigade (light infantry) and RAAF base Townsville (home of the Army’s 5th Aviation Regiment).
Darwin is home to 1 Brigade (mechanised) and RAAF base Darwin (which is a major air base used by Australian and US aircraft – including B-52s and B-2s).
Places up in The Wet (such as Townsville, Cairns, and Darwin) are cyclone prone. Retreats in these areas need to be able to withstand the worst category 5 cyclones.
On balance if I was looking for a place on the east coast of the mainland, I would be inclined to look at the coastal hinterland of Queensland north from Rockhampton up to Cairns (600 miles {1000km} north) . It is far enough north of Brisbane’s population cluster and far enough south of the Torres Strait to avoid a potential influx of people from Papua New Guinea. It has good rainfall and soil fertility. The people tend to be more independently minded, pro-gun, conservative and Christian. Think of the Bible Belt of the US with the relaxed Aussie attitude. (See map.)
The distances to get to even Rockhampton from Brisbane, Sydney, and Melbourne are huge (400 miles {650km}, 750 miles {1200km}, and 1250 miles {2000km} respectively). Living in in those cities (or on the coast between them) my first choice of G.O.O.D. vehicle would be sailing boat (which could also open up other retreat areas such as Tasmania or New Zealand).
Being in the Navy with access to (and having helped written a few) classified studies into mass illegal immigration scenarios I’m limited in exactly what I can say. I will say this: if I was looking at a retreat in the north or north-west of Australia I would locate my retreat at least 60 miles from the coastline. – Mike McD