Nice link Geo. The Montreal Rooftop Garden Project (mentioned in the article) was one of the first places I went in researching urban gardening techniques for my own rooftop. It also is a main link from the Chicago Green Roof Growers blog. Here's their link:
http://www.rooftopgardens.ca/ and a short video:
http://video.google.com/videoplay?docid=-8278820463855564435&ei#Montreal definitely is ahead of Chicago in this regard. It's interesting to note that Chicago also has an abundance of flat roofs and our climates aren't that dissimilar. Hopefully, they will continue to inspire other urban gardeners.
"It's not that I'm on commission, it's just I've sifted through a lot of stuff and it's not worth filling up on the bland when the extraordinary is within equidistant tasting distance." - David Lebovitz