It was mentioned by another poster that Sumpter Valley continues to run in fire season. Having a good deal of knowledge about that operation I would like to point out that SVRy takes pretty aggressive and expensive measures at fire prevention and detection. An A4 motor car with a trailer hauling about 300 gallons of water follows each train. In the higher levels of fire season two fire patrol qualified people operate this unit. The trailer is equipped with a modern high pressure fire pump, a good amount of 1 1/2" and 1" hose with appropriate fittings, enough fire tools for additional crew members such as shovels, pulaskis, McCleods and bladder bags. During the highest levels the fire patrol checks the ROW multiple times between trains. In addition the rr has a 6000+ gallon water car set up for fire fighting with another high pressure pump, 300' of 1" rubber hose on a reel and also the capability to spray the ROW with mounted nozzles. This tank has the dome cut down so it can be filled rather quickly at the water tower. In addition the rr maintains a cache of additional fire supplies including a spare pump. Each season a review for all participating crew members is given either at the least as a self study hand out, or a class sometimes with hands on operation of the equipment. Some years actual burning exercises have been carried out with professionally trained fire personal leading the class.
I have no knowledge one way or the other about why trains are not running on the Wallowa Union, but I would say that Sumpter Valley would be a tough act to follow without some considerable investment in equipment and training of employees by the WURA operator. It is hard to believe that the RDC cars would present much of a fire hazard, but the GP7's are certainly another story.