The Empire Builder does a same-day turn in Seattle. If the tracks aren't open to deadhead the consist up to Everett, that morning's 7 consist is marooned in Seattle and there is no way to provide equipment for train 8. Then the only way to provide service is to short-turn the inbound train 7 in Spokane and bustitute. That most often happens the day of the slide.
When the tracks are clear but a passenger train moratorium is in place, they deadhead the consist between Seattle and Everett and provide service from Everett. That is most of the time. When the line was virtually closed throughout December, service was mostly provided from Everett.
When I took in December, there was another slide that occurred after the deadhead had already left Seattle, so the train was held around Edmonds. BNSF ultimately cleared that slide, and the Builder consist moved through the slide area at walking speed. The train actually pulled into Everett for boarding at midnight. I was afraid they wouldn't be able to get through and be bustituted at Spokane. I didn't care that it was late, as long as they didn't put me on a bus. Amtrak crew management was also smart, as they had a new crew take over at Everett, so the original crew wouldn't die on the law.