Hank, et al,
As far as I can tell without my books handy, the Pitkin branch ended operations before the Lake City Branch. I'm looking at a Fall-Winter 1932-1933 timetable. It still has service going to Lake City, but no service to Pitkin. Also, Jerry Day (as I recall) has mentioned to me that C-16's were only power on Baldwin and Pitkin branches. As to 172 being kept around, photos also show that it ended up in Salida before being scrapped. I would speculate that it may have been backup power for Lake City line. In fact, there is photo of 172 on Lake City train about 1930 meeting Salda-Montrose train at Sapinero.
I still feel that the T-12's saw their last regular use on the D&RGW by the summer of 1933 except, of course, 168's brief movie work on the Santa Fe Branch. I say this because I know of no other photos of T-12's in action after May of 1933-- the only exception being 168's movie work.
Surely would be nice to see some daily posts from Mr. Blouch on this time period to see where the last use of the T-12's occurred and what was the last regular power used on some of the more obscure branches like Lake City, Pitkin, La Madera and Pagosa Springs.
Bill M.