It's been a while, but I do remember some people here on the forums asking if desctructible bridges would come into play in Far Cry 3. Well, I never heard any confirmation of it, but I think I may have some proof.
In the gameplay trailer, at the scene when Jason it riding his jet-ski around the shark in the water, in the top-left of the screen, you can see a destroyed bridge. Whether this was done by Jason or an AI, or whether it's just fancy scenery, I have not a clue. But it's hope.
P.S You may not think this subject to be very important, but I do. :P I take bridges very seriously. It can mean a way funner free-roam experience, setting IED's on bridges.