I was looking at the maps for both Fury Road and in the video game. If you overlay the location of Gastown, it adds further evidence that the location is on the western coast of Australia near Rockingham. The game starts in what was once the ocean bed, this is most likely the Indian Ocean. You head north to Gastown which is most likely the BP Kwinana Refinery. This is where the game map ends and the movie map begins. The Citadel is northwest of Gastown and they headed east, which that would have been put the Green place in what is now the Mundaring State Forest. There is a small island that could be the location of the Citadel in about the right location on the map, Carnac Island Nature Reserve. With the water gone, it would appear as the Citadel appeared and would account for the large amount of green on top of it.
I read somewhere that there were clues in the game as to the real world location, they were leaving it up to the players to figure them out.