The Lake Shore's consist rarely changes. The only variables are the occasional extra coach for peak periods, and sometimes the Boston sleeper getting blanked and replaced by a third sleeper out of New York.
What happens to the BOS sleeper pax?
When that happens, they usually ride coach to Albany. Sunnyside yard adds a third sleeper to the NY section, so once it get there, the Boston sleeper passengers transfer into that empty third sleeper. Then Chicago fixed the order of the consist when the LSL gets there.
The sleeper pax still get their free meal in the cafe and probably receive some compensation for the loss of the sleeper for the first few hours.
Not necessarily. In March 2011, I traveled CHI-BOS and was initially ticketed on 448 in a roomette. The day before I left CHI (actually MKE, but anyway) I was called and told because of a mechanical issue I would be in a roomette on 48 CHI-ALB and coach on 448 ALB-BOS. The SCA (or TA-S) did not seem aware or concerned that I and a few others had been bumped/moved into a sleeper on 48 and had to move to coach at ALB. I had been hoping the crew would let me (and the others) move from sleeper to coach without getting off the train, but we were required to get off and the re-board from the station with 448 passengers originating in ALB. Not too big of a deal, all in all, and I did get some sort of a refund of the ALB-BOS portion of my fare.