I've taken the train from BBY to NYP maybe a hundred times and never once seen my ticket checked or others' tickets checked. I think that would go double on Thanksgiving given the massive crowds that are likely to be in each station. (I've also hopped on from BBY to BOS a couple of times, truthfully, although not recently.) I also don't recall seeing tickets checked before the train departs 128, although if that did happen, I think you could just feign confusion and get away with it.