There will be no fighting on the ruined bridge. All the fighting will be on the other side of the bridge. It will be a gold map too.
That's a huge exaggeration, Mordor usually did get past the bridge, and overall Gondor and Mordor both won at around the same rate.
My favorite map Really though, the bridge stalemate is often exaggerated. It wasn't usually that bad.
But once they passed the bridge their would be no more fighting because everyone would get stuck or lost in the ruins.