Herb
There are more photos out there than have been put in the books. Yes, I have seen several photos of an engine running in reverse on a rotary train. Look at Doris Osterwald's "High Line to Leadville" book on pages 50 and 51. The book is mostly about the C&S, but there are three pictures of Rotary ON on the Blue River branch and one of the engines is running in reverse. I personally have photos of them doing that on the Floresta branch. It seems to be an early day practice that did not carry over into later years.
I think it might have been because the early day rotary trains did not have outfit trains with them. The practice was to tieup at a section house or depot. Rotary ON and OO never had outfit trains like OM and OY.