In front of my apartment, there is a patch on a patch on a patch on a patch on a patch. They rebuilt the street in the 1990s and didn't fill it properly so it caves in a little around manholes, and they patch it. It gets less bad every year, so the patches get smaller and smaller over time. I would guess that the asphalt around them is close to a foot thick by now. With our warmer winters, the cracks have been getting worse at a faster rate. This is probably what Toronto experiences.
We always complain about our freeze-thaw cycle, but it's only a few weeks long. Toronto's freeze-thaw cycle is almost half the year.
We do have one street on a hill in the north end that was repaved improperly so the asphalt slid down the street while it was still hot, it's weird.
http://www.opinionatedbastard.ca/?paged=6
The company that did this is a small contractor that was responsible for doing all of our streets, (we contract out all street projects, about 40 per year, to a single bidder in a single contract) and they had trouble actually doing what they were paid to do.