|The following is based on information from Van Buren design documents and is not canon.|
The ghouls in the Reservation need an elevator cable. Make sure there's a salvageable elevator cable in Denver they could use.
Near the seemingly abandoned railcars is the Equipment Lift and the Main Access Elevator. The Main Access Elevator is very similar to all the other vault elevators in the other Fallouts. It will take the PC to sub-levels 1 and 2, but not 3.
The Equipment Lift is a large, steel platform elevator that goes directly to sub-level 3 and can only be operated from the 3rd sub-level. Both elevators are working and well maintained, however, the equipment lift needs a new cable in order to function – the engine works, just no cable for the actual lift.