I visited Old Tucson earlier this year, specifically to see the old s.g. locomotive. It is derelict, but mostly intact. This was used for some old TV shows (Little House on the Prairie?). To show the engine running the other direction required turning it with a crane.
I saw no evidence of any trestle.
Tombstone, though, did have a s.g. railroad, and some of the trestles are still intact. Dry washes abound. I don't know if any movie rail scenes were filmed there.
It'd help if you could remember the movie....