You wrote: Virtually all of the Oregon traffic went to the SP. Only small percentages went to the other roads in the state as long as the SP provided acceptable service.
Not entirely. There was a LOT of lumber coming out of Oregon, I will not debate that.
However, the Oregon shippers seemed to be a testy lot. And that led to......
A letter (STMFC era that I have a copy of) from the president of the SP to the president of the NP promising him that whatever useable empty boxcars he can divert to the SP and Oregon, he will get back as carload shipments east. There were car shortages all over the PNW and the SP and NP had quite friendly dealings and often helped one another.
So much so that the president of the NP would often spend the winter holidays guest of the president of the SP. Jim Dick - St. Paul