Morganza stated in the other thread, that:
You can always run the Ghan, as long as you have a route to Alice Springs.
But in a recent game, I happened to think, doesn't the same rule about having different tracks when running more trains apply to the Ghan?
If the Ghan needs different tracks to run to Alice springs, I think its value to certain companies drops. In the game I had to work hard to get my Ghan to the Alice springs through another route, since my other train was using the most natural track.