Keeping Old Buildings?

On our recent trip to Montreal we were told that in Old Montreal they are not allowed to take down old buildings. It certainly makes for some great renovations...and also some 'interesting' ones:

Here's a restaurant behind a façade (after a fire I believe).

Edmonton could certainly have gained from not destroying the old courthouse in 1972, and the Tegler Building, and...and...and...  (see link here for some lost buildings in Edmonton).

Nice to see a 'bit' more saving of old buildings in Toronto, but it's a whole different (legislated) level in Montreal (or at least, in parts of Montreal).