Is there resident permit parking in this area? If so, the way to enforce car restrictions is to make the address ineligible for a resident permit.
There is only scattered resident permit parking in Newton, not much of it near this site. Instead, parking is constrained around there by being metered, and forbidden overnight. And overnight parking is forbidden nearly everywhere in Newton during winter months, to keep clear for plows. So, if the six apartment units had no spaces on site, the lack of available nearby street parking would be a de facto form of a car ban regulation - via pain in the ass factor. Again, it's six units: as a nearby resident, I'd be completely ok adding six cars to the local mix in the name of boosting affordable housing stock. And I would certainly hope the residents would use the T a lot. I use the T a lot, and the wife and I only have one car as a result - but doing without that one in Newton would be a real burden. I'd be very leery of demanding that lower income folks make it work just to spare us more fortunate folks a measly six cars, some of which would probably be used mostly on the weekend, like ours is.
Hotel patrons are more likely to use taxis/Uber/Lyft. They don't take up parking spaces but still create traffic.
Very true in a downtown hotel, but even they have a bunch of parking, because even there some patrons show up with a car. I find it hard to believe that any hotel operator will build 57 rooms in Newton Center without onside parking for a bunch of them, if not all of them or nearly so. If events prove me wrong, so be it, I'll be happy to be wrong on that point. But the more I think of a 57-room hotel there, the less I perceive it as likely. A boutique hotel, sort of bed and breakfast style, with about 16 - 20 rooms would work great there, especially if the "breakfast" part of the deal was a certificate to the abutting restaurant rather than cramming the usual kitchen/dining facility into the hotel building itself. I'm just really curious to see how they're getting 57 units on that site. I'm possibly going to be able to make it to the Friday morning presentation, if scheduling adjustments allow.
I spend radically less time worrying about traffic than most Newtonians, so my attitudes are not representative. My neighbors will squawk about the traffic impact of a hotel whether folks arrive in their own car, or, as you suggest, via Uber/taxi/Lyft. So, yeah, there will be a NIMBY response.
More generally, I'm glad someone's proposing something to convert some asphalt to a building. The more this happens in Newton Center, the better.