Unsure if BNSF made agreements with Yakima or Ellensburg; they did make a " Gentleman's Agreement " with Auburn,WA to limit the number of daily trains. The joke's on them, however. The Stampede Sub, as currently configured, cannot handle many trains anyways. Long stretches of single track, including 19 miles of the worst grade, and most sidings under 9000 feet, along with Track Warrant Control, make for long gaps between trains.
Dept. of Irony; the Northern Pacific essentially founded the City of Auburn; their yard & shops were one of the largest employers for years. Auburn fought the BN merger, fearful the the yard would be closed. ( took BN 10 years but they did it...). Fast forward to 1995; when BNSF began planning to reopen the line. Now, the City of Auburn fought to prevent " the abandoned line " from " reopening. " Fact is, the line was still used out of Auburn, to a coal loadout in Ravensdale & to a ballast pit in Veasey. ( near Palmer Jct. ) The RR played the Federal Interstate Commerce card, and shut the City down.
Maybe there's a lesson here for the folks in NorCal, along a certain " Abandoned " rail line...