This is one of only three bailey bridges in the Greater Toronto Area. This particular bridge (in Markham) dates back to 1954. It was built by the Canadian Military Engineers in three days after Hurricane Hazel hit Toronto and washed out the original bridge.
Although hard to see in the bottom image, the bailey bridge does not actually make contact with the original bridge foundation.
Interestingly, bailey bridges are usually considered temporary structures but this bridge has been in place for 60 years.