Hi Mike,
You're probably not going to see a lot of NG sunset shots outside of the charter environment, as most of the regular trains are tied up long before sunset. The C&TS does run some evening dinner trains to Cumbres Pass in the summer, and that's probably the best that you'll get shooting regular operations.
WRT charters, this is probably the best sunset I have. It had been a mostly cloudy day, but we stopped at Apache because we could see a gap between the cloud deck and the horizon and we thought we just might get a minute or so of "drop under" just as the sun was setting. We backed the train up and started him while it was still cloudy. The sun popped out just as the train passed the crossing and headed west. This was the result:
Apache Sunset
/Kevin Madore