I wouldnt be surprised if it's the first step in getting non-electric motorized bikes out of the bike lanes completely.
Using a ped to bomb over the Mass Ave bridge (or any bike line) during rush hour is one of the best perks of riding in the city.
Since every other college chode in town now has an E-bike, Im sure keeping the moped kids and the gacked-out chinese scooter junkies outta the bike lines will be the next restriction after requiring plates.
Fuck it, if you see a cop just act like you're pedaling and im pretty sure 9/10 times they won't look twice.
I ride with a retro West German plate and just act like I'm old and don't know any better. A transit cop asked me about it but just out of interest, not that he gave a fuck about legality.