Thanks all.
The XPT SYD-BNE is indeed temporarily suspended between Casino and BNE doe to track upgrade works.
http://www.queenslandrail.com.au/for.../trackclosures
But I saw that Casino appears to have a nice green environment and is dark as well according to DarkSky finder.
http://darksitefinder.com/maps/world.html
So taking the XPT to Casino and renting a car there (I found out) and staying in an AirBNB around can be an option.