That's pretty likely, yeah. (Other trains weren't having problems.) I know there are switch heaters that help, but if a big chunk of ice does fall into a switch it would take time to melt.

Also, remember the article in Trains about snow in British Columbia? The next issue someone wrote in with a picture saying "it's not just frigid Canada"; the letter (and picture) was about an irritating-looking derailment on the north side of the drawbridge here where an inbound train kind of went straight through the snow where the switches were set to "turn right". Oops. But now any sort of winter trouble around North Station makes me think of that.