I noticed that the bridge that carries a local street between Sainte Helene Island and Notre Dame Island in Montreal was once a cable stayed bridge back during the 67 Expo and now the towers are still up but no cables. I am guessing that it had to do with the fact that the Expo Express, that was a rapid transit train that was used during the Expo, is no longer tracked on that bridge anymore. It used to cross the waterway there with the car roadway along side. The train cars obviously weighed plenty and being the lack of piers under the bridge it needed the cables as well as provide the "Bridge of the Future' at this World's Fair. Then again it might not be but a facade.
If you look at old photos of the Fair and go to Google street view for the latest you will see the change.
For those who are wondering, he's talking about Pont des ÃŽles, located just after Pont de la Concorde, on Avenue Pierre-Dupuy.
http://maps.google.com/?om=1&t=h&ll=45.506467,-73.537674&spn=0.016572,0.034761
Most of the weight of a bridge is the dead weight - the bridge structure itself. A train is a significant live load but not to the same degree. I haven't heard of a cable stayed bridge being built to stand up without the cables - something seems wrong here. The structure itself ought to require cables just to handle the dead load, or else it was overbuilt to the point that the cables weren't necessary in the first place.
According to this page (http://expolounge.blogspot.ca/2008/08/expo-bridges-concordia-bridge-and-pont.html) and this one (http://www.flickr.com/photos/61779764@N00/2524899351/), Pont des ÃŽles had to be rebuilt in 1997 because of a structural failure, and that would have been when the cables were removed. The bridge was converted from hybrid rail/road to road-only in 1975.
The deck is still 94 feet wide (5 lanes + 1 bike lane + 2 sidewalks) after reconstruction, even though it bears 2500-3000 vehicles per day. The maximum density of the road is at least 5 times its peak density, and its capacity is at least 10 times the actual rates, according to a recent study by Dessau.
Some illuminatus proposed a tunnel under the seaway canal to link downtown Montréal with south shore using the Pont des ÃŽles : Tunnel Centre-Ville - The Way Ahead (http://www.investissementlucpoirier.com/en/projets_tunnel-centre-ville.php).