The RMV does require lettering for commercial vehicles. Most police do not enforce the law though.
However, there is a cop in Woburn MA that does give out tickets for $1000 for the offense (no, I did not accidentally add a zero, one thousand dollars). I know a few people who got tickets but then fought it and won probably due to the mercy of the judge.
I do a lot of work in Boston where you need lettering to park in commercial parking spaces otherwise I would not have lettering.
