John:
According to my notes (from newspaper accounts and Bob Richardson's Narrow Gauge News), OY was used again in March.
57 was the year that got all the news coverage because they were able to photograph from choppers and planes, but the worst year on Cumbres was 1932.
A retired D&RGW engineer who either ran or fired rotaries ON and OO out of Gunnison, said he hated working on a rotary as they were cold inside (snow came in through all the cracks) and noisy as all get out. He was on the last run of Rotary OO in 52 and it was so cold the Jack's Cabin water tank froze solid and they had to return to Gunnison before they were done as they ran out of water. They were planning to come back the next day to finish, but the D&RGW used wedge gon 09271 and Spreader OV to finish the job.
The rotary runs are a lot of fun for us railfans, but the crews couldn't wait for the snow to melt.