I think this model is called a canopy. They were installed where the sidewalk isn't wide enough to permit side wall without impeding pedestrian traffic. Astral stopped installing them, I believe, after complaints. The solution was to not to put in any shelter at all at this type of location. There was a Fixer article about these shelters back in January: http://www.thestar.com/yourtoronto/the_fixer/2013/01/17/the_fixer_say_goodbye_to_onesided_transit_shelters.html