It is a Chicago - New York (Pennsylvania Station via West Side Line) train. For many, many years, coaches and sleepers were switched out at Albany Rensselaer for the Boston connection, but I have been told that passengers must change trains now, for some time. I believe some NS trackage is used between Toledo and Chicago – through South Bend abd Gary, for example. Here NS is on the old NYC.
Not really, the information is also contained in the Amtrak Timetable. Boston to Albany is train #448/449 that connects with sections from NYC (train #48/49) and Poughkeepsie, NY (5 different train numbers). Boston and Poughkeepsie to Cleveland is owned by CSX. Cleveland to Chicago is owned by NS.
This is normal, scheduled routing, not anything to do with detours.
On the subject of the Lakeshore, I saw it on Saturday (10/27) in Springfield, MA. It had no baggage car (which I wanted to see) and only two Amfleet coaches and a cafe car. Seems like a smaller train than what they usually run. Oh well, I guess there was not enough riders.