Bill,
From what I remember the C&TS has allowed Speeders on the line. It was the same group that was on the D&S during RailFest then traveled to the C&TS and ride the line over there. I was on the C&TS the same day the speeders were there. They left VERY early in the morning and we rode the bus to Antonito and rode the Train the entire length. At some point they were all in a siding waiting for us to pass.
You do have to belong to the Group and I used to have the URL I'll try to dig it up.
They plan trips around the US every year. Both Standard and Narrow Gauge.
Kevin