The idea is that they have taken pathetically ugly suburban sprawl, and illustrated what it would look like after improvements. Trees, sidewalks and light rail are added, and the form of buildings are changed to make them more urban. It is worth going to the site, clicking on one of the examples, and stepping through a few images (by clicking "Next Photo") to see what happens. Note the TTC streetcar in Oakland, California.
In each case, the thing that makes the biggest difference is the addition of infill development of new buildings close to the sidewalk. The trees, the parked cars, and the pedestrians help a lot, too.
To me, unfortunately, it all just looks like an exercise in throwing around pretty props. Ignoring the political and economic difficulties, these transformations are still impossible to do on a large scale. What is shown in these examples is nice, but where are all the buildings and people going to come from? There are hundreds of kilometres of boring suburban avenues here in Toronto, and to convert them all in this fashion would require an absolutely enormous increase in population. Either that, or we would have to condemn large swaths of outer suburbia, and relocate people into a denser inner suburbia. That's the thing about low-density development -- it takes up a lot of land. To fill all that land with density, you really need a lot of people and a lot of stuff.
There is no doubt that these before-and-after pictures do a good job of showing the difference between what was built and what should have been built. But they do not show a viable blueprint for how we can transform all of our suburban ugliness into a people-friendly city.
However, there are parts of the City of Toronto where it may be possible to do this. In fact, on places like Kingston Road or Sheppard Avenue this is exactly what the city's new official plan hopes to do.
[Update -- David at City Comforts responds here.]