It happened to someone I know—TWICE. Two years apart. His car was registered at his dad's house, and he was living elsewhere, so he wasn't getting the reminder notices, and for some reason his dad didn't forward them. You'd think he'd have learned his lesson the first time, but no. I know that one of these incidents involved the police in Groton, and the other time might have been Westford or Chelmsford, or possibly Lowell. Either way, yes, they will impound your car for this.