I'll email Consumers/Enbridge and see if they know. I suspect that I will not get much by reply, but I hope they surprise me.
Urban Shocker, they are both gasometers that rise and fall depending on the amount of gas within. If you look in the photo at the vertical supports, you will see a sort of swan-necked arm that goes form the top of the holder to the support. That has a wheel on the end of it that rides in a channel in or on the support. Condensers, cleaners, etc., did not have that as they were fixed height.
SeanTrans, the bridge is still there. When the alignment changed they pulled the bridge into the new alignment with a locomotive.
Fascinating stuff, had I seen taht photo elsewhere I would never have thought that it was of Toronto.