Telephone Booths

Hi Guys,
I'm curious about the two phone booths on the C&TS, Coxo and Cresco. Was this type of building common throughout the system? If so what was the reasoning behind their locations and how would the crews have used them? Were they normall just used to report problems and if so are they placed in areas were problems are common? I guess they really are phone booths even though both buildings show no evidence of insulators or wires. Did the Rio Grande maintain the poll line and wire up untill the end of operations, and if not, when was it abandoned and how did its demise effect operations?
Any info would be appreciated.
Thanks.
Bill