Another factor for sleeping car placement is those trains that switch out cars mid-trip. Currently that is just the Empire Builder (Spokane) and the Sunset Limited (San Antonio). The Builder usually has the Portland section on the rear with the sleeper as the last car of the train, the Seattle sleeper(s) are usually at the front.

Back in the days of the California Zephyr/Desert Wind/Pioneer (aka the Amtrak version of the City of Everywhere) with cars combined at Denver and/or Salt Lake City there were sleepers mixed throughout the train, usually the Desert Wind sleeper was sandwiched between the Desert Wind coaches and the Pioneer coaches.