Upon further review...
According to the Internet Movie Database, the bridge scenes for "It's a Wonderful Life" were shot on a backlot at RKO Studios. The reason that George Bailey (James Stewart) is sweating in those scenes is because they were shot on days where the temperature was over 90º.
So no, this is not the bridge where the scenes were shot.
The Internet Movie Data Base (imdb.com) lists the only New York location for shooting as Ithaca. I'm not a movie historian, by any means, but I suspect the bridge in IAWL was built on a sound stage.
Any movie historians wnat to take a shot at this one?
Is this the bridge that was filmed in Its A Wonderful Life?