The westbound BN-137 (WP used the BN symbol) would arrive Stockton with either all or some of the consist bound for interchange with the Santa Fe. If the entire consist was ATSF-bound, the road crew would run their power around the train and drag it over to Mormon Yard (where one frequently had to wait a long time for a clear track to get back), then shove their caboose back to the WP yard. Being on Final Terminal Delay, this could be rather profitable.

Otherwise, ATSF-bound cars would accumulate on a track in the yard (Track 15, IIRC), and would periodically be taken to the interchange tracks, which were located along the WP main between Charter Way and Stockton Tower. Sometimes, a WP yard job would take cars all the way over to Mormon Yard. Conversely, Santa Fe crews would bring cars into the WP yard, as well as spotting them on the interchange.

WP-SP interchange took place near the middle of the two yards, which were parallel (actually between the two railroads' main lines). However, WP-SP interchange was quite insignificant compared to that between WP and Santa Fe.