Now...for the issue about the enabling wearing offf.. You would have to do a series of triggers that give the cannons owned by a player and give it to the
town computer enabling them and giving them back to that player and going on to the next player.
Of course, i've never tested this it is just an idea i threw up in the air.

Scientifically, it should work, but the editor doesn't always give you what you want.
Evildrone(U) had a good method to deal with this problem. What you do is when you create the cannon also create a lurker (or other burrowed unit) at a remote area. Then move the burrowed unit under the cannon. This burrowed unit should be owned by the "town computer" or something inorder for it not to interfeir.
Anyways when you have a burrowed unit under each cannon you can Give the burrowed unit away one at a time while centering locations on them and enableing the cannon above it. When you gave all the burrowed units away simply give them back to the original player.