It is possible that the brotherhoods did, both the shop union and the brotherhood of locomotive engineers I don't know the details though.
Some of the firemen working out of Durango in 1967 were Dave Rentfro, Doug Rathjen, Robin ``Rowdy'' Yates and (no first name given) Rossi. It looked very easy for Durango to run out of men.
Bob Shock and Steve Connor were on the Silverton with Andy Payne and Don Gibbs on freight as engineers. That would leave the other four as firemen. Fortunately for the crew caller there weren't that many freight trains.