Here is a link to someone selling the toy that does a good job of describing the product. It seems to work a little differently being designed to use woodboard cut outs as the figures rather than those of the Richard Scarry sets. Sesame street uses little green feet pieces that hold the character pieces.
The houses themselves use foot and roof system. The roofs are single piece rather than build, as in the Richard scarry sets.
My original post on puzzletown can be found HERE
I just wrote up a third post on puzzletown and you can find it HERE
There is also a brand new post here.