I think there were recent plans for streetscaping DT Crossing that involved pedestrianizing a lot of the little streets between Washington and Tremont.
Boylston is too wide and essential for traffic for this to be contemplated on.
In fact, I get nervous jitters thinking about downtown Buffalo when pedestrianization schemes get too bold. The city, like many, banned cars from its main downtown street in the 1970s, and today it's virtually deserted. Although the desertion was obviously caused by other factors as well, there is strong advocacy for turning the street back over to limited auto use, if only to increase convenience to local businesses and to impart a sense of "busyness" to the street again.
I think Times Square will miss that as well. Streaming (or honking) traffic was always part of the landscape there. It's part of the excitement of urban life, particularly in North America. What works for a 16 foot wide medieval street in Italy won't always work best here.
Whatever happened to compromise solutions like the woonerf, where cars are allowed to tread (slowly) on streets essentially designed to maximize pedestrian utility?