Based on nothing but my SWAG and rumors ....
If Mt. Rainier Scenic suspended operations due to the 416 Fire, I would ASSUME (with all the pifalls that comes with it) that the MRSR is expected to operate at a loss and is dependent upon being subsidized by the D&Sng. You would hope that the MRSR could have at least run weekends using a skeleton and part time staff, but it could be that the available labor market and/or advance reservations suggest that they would face a difficult time even covering their direct avoidable operating costs (fuel, train/ticket/sales and related maintenance labor/costs). It may be that their normal train operations are struggling with ridership, though they've made it clear that their special event/themed trains will run this fall.
So far, it doesn't seem to have affected their Great Smoky Mountain rail operations. I see that D&S is now saying no coal fired steam trains through June 30th, but still leaving the possibility of limited range diesel powered trains before then. Until the fires die down enough for the smoke to clear out, I don't see much of a public demand to ride the train or visit the area anyway.