I rediscovered these photos in an old file. A Google search brought up the official accident investigation report which I hadn't seen before:
http://www.atsb.gov.au/publica...air/ro-2010-015.aspx
The gist of the report is that a recently installed siding ("crossing loop") had rail misalignment exacerbated by high temperatures and insufficient ballast etc.
Some of the vehicles have eastern states license plates, possibly used cars being transported west to markets in Western Australia.