Sounds like a great idea, and in any country but the US it would probably be possible. If you closed the gate and did not allow traffic though and did not have anyone on property that had not signed some sort of release it might work. I think that the liability otherwise would be too high. The other problems would be insurance and what equipment to use. The insurance companies would probably have a fit if anyone was running trains that had not had all the proper training. However, I know that at the D&S anyone can run equipment as long as it does not leave the Durango yard, the gate might have to be closed as well. On private property you can do anything you want. As far as equipment goes, the rod engines at the CRRM are pretty small from a railroad stand point but huge compared to what most people operate every day, most people would have difficulty stopping fast enough. One of the Geese might be a better choice because it is a familiar format to most people. I'd pay to run Goose 6 around the loop a couple of times. The other options might be PeeWee and D&RGW #50. With 50 being rebuilt I’ve wondered if they could do weekend operating sessions over the summer, assuming that volunteers could be found to operate the train. Then do steam trains on special occasions. But I digress, I think that a drive a train type day could work if if was given the planning and volunteer support such a project needs. The final problem(last one I promise) might be that such a day would interfere with any normal volunteer work that might be happening that day, and so the income from the event would have to offset that cost.
My 2 bits,
Paul