A few years back during a previous STAR, I rode to the top of Bald Knob on the Cass Railroad and it seems as if the entire train was reserved for us. It was our Tuesday Lunch Ride and was great fun.
This year at Fall Colors, Deb & I are taking the ride up Bald Knob on Friday, Sept 29, in case anyone wants to join us. They have one run that leaves at 9 AM and another that leaves at 11:45 AM, we're on the latter, with the total time for up/down being 4-1/2 hours but they have to stop for the locomotive to take on water partway way up/down so the actual time the train is moving is closer to 3 or 3-1/2 hours. The Bald Knob run includes a "hobo lunch" which I presume is eaten at the top.
You can get reservations at the Cass Railroad website or maybe buy them onsite that day but I wouldn't rely on that method because you might be disappointed.
And if you haven't visited the Greenbank Telescope facility, it's well worth the stop...just leave your microwave ovens at home! Two more reasons to attend Fall Colors!