Re couple of thoughts...

Coxo's existance has always baffled me. It is only 1 1/2 miles from the top, less than a 10 minute run. Cumbres' yard capacity varied between 70 and 105 cars over the years. Arranging a meet at a blind siding 1 1/2 miles down the hill seems real odd. Getting a freight rolling downhill around that curve stopped to line the switch would be fun. In general, passenger trains never went into the siding to meet freights unless the freight was too long, in which case I'd think they's hold it at Cumbres for the passenger.
Coxo sits in a place where the snow gets REAL deep in the winter. Some of the hardest plowing I did was through Coxo. The tall trees block the sun and the snow never melts.
In later years, the Grande set out flats of ties for unloading here. Coxo was the local tie storage spot. It was out of the way and far enough from a road to discourage the ties from wandering off. On the east end, Lava siding (not the loop track) served the same purpose.
Coxo was removed in 1965.
Now for the logging idea....
I doubt there were any logging areas of much value up Wolf Creek. It gets real steep real fast back there. An area that makes more sense is directly south of Coxo. The terrain is rolling hills which would have made skidding the logs to the RR easier. Again, there isn't much area to be logged though, certainly not enough to justify a 15 car siding. Also, the logs would have to be hauled across the mainline and loaded on the siding.
Lastly, looking at some of the shots Bob Turner came upwith for his recent book, there is a great shot looking down off Windy Point very soon after the RR was built. It shows scorched earth. The Osier fire of 1879 appearently did cross the divide and head down Wolf Creek. Today there is a beautiful aspen grove just south of the RR after it crosses the highway and heads toward the siding location. In 1880 it was a baren field of burned and downed snags.
So... what does this all mean? Nothing, just an observation. Anyone with real evidence out there??