I have a recollection of seeing that photo, or a photo of that ambulance, somewhere before. I can't find it right now, after a quick search. But here's another rail ambulance with the same branding, this one taken at Tullah, on the Farrell (or Tullah) Tramway. Photograph courtesy Tom Murray.[img]http://i164.photobucket.com/albums/u23/duttonbay/Odd%20Photos/02511Jun1961_zpsf74cbc2f.jpg[/img]
Edit: Found it! The ambulance in your photo was the Emu Bay Railways, and remained in service until 1961 when the Murchison Highway was opened, connecting the various settlements on the West Coast by road. The Farrell Tramway ambulance in my photo existed for the same reason - the tram was the only way out of Tullah in the event of someone needing medical attention, and also lasted until 1961. The photo and description I found was on p173 of "The Emu Bay Railway, Centenary Edition" by Lou Rae.