Not in Australia, but here is one of our fellow collectors who I think now has at least four of these bomb trailers. Picture below shows one being towed by a Clark Airborne Dozer something a little smaller than yours. The Bomb on the trailer is a nuclear practice bomb. Steve often tows it around to parades or local cruise nights behind his Chev Bomb Truck or his CCKW. Here is a link to some pictures
http://www.cckw.org/ww2_vehicles_2005.htm or go to
http://www.cckw.org/mvmvc_weare_rally.htm pictures from the last three years of Weare, NH Rally. For a interesting CCKW web site go to the root site
http://www.cckw.org/ .