Control Point (CP) Information

During a recent trip on the California Zephyr through UP territory, I observed a standardized format of identifying control points (CP). Sings attached to the physical plant used the following example: CP 280 RG Glenwood. I presume 280 represents the distance from milepost 0.0, RG represents the "historical" railroad (in this example the Rio Grande) and Glenwood is the location name. While on the segment between Denver & Dotsero, the signs showed "DS" for the segment. I assumed DS represents Denver & Salt Lake City while the conductor thought it represented Dotsero or Dotsero Cut-off! Does anyone know the correct information and what are other codes are used by the UP across their system?

On the UP, the codes for CPs vary by subdivision. For example,

AL on the Alhambra Subdivision
SP on the Fresno Subdivision and Gila Subdivisions
SA on the Valentine Subdivision

and the list goes on and on. I don't know of a single source for all codes for all of their subdivisions.