I've seen the solar-electric compactors in front of Faneuil Hall (on the Sam Adams statue side) and on Hanover Street in the North End.
Theyre also on Boylston street, near the Pru, and all around Fenway Park.
They're from a local company, and the city started a trial with them a year or two ago. I guess they liked it, because I see them in more and more places. They have two models, a large green one, and a smaller black one for places like the north end.
They have a solar panel on top which powers a compactor, so it can fit as much as 3 regular garbage bins. The other benefit is that its closed like a mailbox, so once trash is in it wont fly away.
The lack of this on comm ave tells me that soon the new stone will be chopped up for hundreds of ugly parking meters instead of the newer parking machines seen on Newbury street.