I am confused, too, I have never seen Amtrak leave Superliner cars here before. I am not sure if they were part of today's SWC or not, but I assume they must have been, because they are here at roughly the same time the LA-bound SWC would depart here.
If so, I wonder if Amtrak split the train, with the 2 'missing' locomotives hauling the rest of the train further south...maybe a Superliner car was damaged, and they were going to leave it here; reconnect the 2 locomotives and other Superliners with these 3 (that if my guess is correct were at the end of the train, behind the damaged Superliner), and continue on to LA?
I assume they wouldn't drag 3 empty Superliners here to leave them overnight and be picked-up by tomorrow's Chicago-bound SWC?