I think the WV State Railroad Authority may use both models. I believe they operate the South Branch Valley RR directly, but the former WM line from Elkins to Spruce is operated by a designated operator, the Durbin & Greenbrier Valley. The D&GV also operates a short segment of the old C&O Greenbrier line, from Durbin towards Cass. They use a two truck Climax on this line.
Earlier online posts seemed to indicate that the Durbin & Greenbrier Valley might be the ones to assume operation of the Cass Scenic, but the current article sounds like the Authority may be the operator.
Over the years the State Parks have operated the Cass Scenic with greater or lesser success, depending on the abilities and inclination of the local park superintendent. Some have understood railroad operation, others have not. Running a mountain railroad with 8% grades isn't for amateurs. I hope the right people do end up in charge.
Michael Allen