You can also go to http://geojson.io and load the generated file for more interactivity (select, delete, add your own polygons, etc.) or open it in QGIS.
In the Results section I had a screenshot of the generated polygons in both QGIS and geojson.io (polygons are separated by thick black lines and their area is colored gray).
Reluctant to respond, since it's clear that bit of more effort went into your comment than mine.
Basically for me when I click the interactive map I get a response, which is a pinned blank text-box with a x to close it. Thing is that I'm unable see that a city block is highlighted via a click; the text box simple appears where I click, unless it's outside the targeted area; for example, in the river.
Looking at the raw JSON it does appear the block are extracted.
So, putting aside "seeing" it, appears you're confirming it extracts single blocks as objects and isn't doing something else like if two blocks are attached, they're not sharing the path that's between them.
I followed my instructions in the post (except I had to use encoding='iso-8859-1' instead of utf-8)
I cropped the map a little.
Generated file https://gist.github.com/pdonald/223e42b491eb42ba99b8e10ef1ae...
Interactive and clickable http://bl.ocks.org/anonymous/raw/d62bfd592234ed71d24bfd6f264...
You can also go to http://geojson.io and load the generated file for more interactivity (select, delete, add your own polygons, etc.) or open it in QGIS.
In the Results section I had a screenshot of the generated polygons in both QGIS and geojson.io (polygons are separated by thick black lines and their area is colored gray).