John, the chart above shows more sightings in the summer than the spring. This is why it's a good idea to look at the data on a local level, preconceived notions are sometimes incorrect.
I have been to Australia and know for a fact that at the time of the story which was 2003 that no handguns such as the Sig-Sauer P226 in .45 calibre were available for sale to private owners in Australia. Target shooters are limited to 9mm or .38 calibre or less unless you are shooting single action or siilouette which the P226 does not fit into. According to the google search I did the Australian SAS and the Commando units used the typical 9mm calibre and to suggest that these bozos would be able to play war games as they did and not get into very serious trouble is ludicrous. The story sounds very much like braggadicio by week-end warriors.