I would imagine the Cascade run would be a good candidate for taking over.
The people who rode that train seemed to be interested in a short train ride and then have the ability to do other things in Durango. So from a foamer's viewpoint, the Cascade run might be the most, ahem, "acceptable" train to be handled by a diesel. Allowing steam to handle the traditional run to Silverton unless fire conditions require otherwise.
Steam could then remain, possibly, on the Cascade run until weather conditions permitted otherwise.