One thing I wonder about the world in which Mad Max takes place is, how long before our story begins were the Forbidden Zones established?  How extensive were they?  Could it be that, although it wasn’t widely acknowledged, the Australian government had actually lost control of large areas of the country some years before?  

Even in our own world, it’s questionable who can be said to control the vast and very sparsely inhabited interior.  A bloke who calls himself Prince Leonard seceded his property around Hutt River in Western Australia, together with that of five families who were his allies, back in 1970.  Now, Prince Leonard is a wheat farmer and hermeticist rather than a water-hoarding warlord, and his heir the Crown Prince Ian farms wildflowers (seriously), but they are an example of how difficult it is for the Australian government to enforce its authority over a determined old bugger out in the sticks.  

What’s more, the Japanese terrorist cult Aum Shinrikyo purchased a large station (Americans would call it a ranch), also in Western Australia, in the 1990s and, during their ownership, there was some kind of huge explosion and a fireball in the sky that have never been properly explained.  Bill Bryson’s book In a Sunburned Country gives the details, summarised here by Cecil Adams of The Straight Dope:

1. At 11:03 PM local time on May 28, 1993, a large-scale seismic disturbance, elsewhere reported as measuring 3.9 on the Richter scale, was detected near the Banjawarn sheep station in remote western Australia. The few observers in the area reported seeing a flash in the sky and hearing an explosion.
2. The blast was 170 times more powerful than the biggest mining explosion ever recorded in the region and was consistent with a meteorite strike, but no crater could be found.
3. In 1995, after the Aum Shinrikyo in Japan had released nerve gas in the Tokyo subway system and killed 12 people, it was revealed that the cult owned a 500,000-acre property in western Australia near the site of the mysterious boom.
4. The cult has two former Soviet nuclear engineers in its ranks, hopes eventually to destroy the world, and maybe wanted a bit of practice, eh?
5. In 1997, scientists finally got around to investigating this disquieting possibility. “You take my point,” Bryson writes. “This is a country … so vast and empty that a band of amateur enthusiasts could conceivably set off the world’s first nongovernmental atomic bomb on its mainland and almost four years would pass before anyone noticed.”

I’m just saying.  You can get up to a lot in the Outback without anyone really noticing.  Constructing a Citadel or a Bullet Farm is kind of small potatoes.