When I got home, I woke up Cat Lady, told her we had a problem, took her to the quarantine room, and said, "Meet Alpo". The poor thing was still not moving. We were not able to remove the can, and couldn't find an emergency veterinarian that would pick up the phone. I guessed (correctly) that a local truck-stop garage would be open at that hour, so we took the cat there, in search of a pair of scissors that could cut through metal. While I was talking to the clerk, though, Cat Lady came in from the car with a now can-less cat.
Alpo was less frantic on the ride home than we would've expected, and socialized well with us once we got home, so we guessed that it may have had human contact before. On the other hand, its fur was highly matted, and it was obviously starved and dirty, with no collar, so regardless of whether it was abandoned or feral, we didn't want to return it to its prior environment. Cat Lady's taking it to the vet after I leave for work today, for its shots, de-flea'ing, gender identification and a full-body shave; neutering will follow later. Hopefully we can integrate Alpo into the rest of the cat family, but we have high hopes, given how affectionate its been since it can see and move.