With 3.02 patch5 the bridges work.
I can set the shore on each side of a river to different elevations, and place a bridge inside of one mile from a square object like tank town. Just have to remember driving down fast off the end of the bridge to hit a radical up-slope will stop your tank and make you have to first go into reverse, then go forward slowly. It works better to feather the shore land down to the ends of the bridge. A little bit of cosmetic touch up.
I set the bridges to be "Runway" which effectively makes then indestructible. You can drive a PT boat under them, but you will have a momentary visual of sailing across the bridge bed until you come out the other side.
Only Hitech can tell me how many bridges I can place inside of a 1x1 or 8x8 area and not harm FPS. Now that this is fixed, I will have to get serious about the water way system around the tank town object and GV spawns. At least you will have the ability to call in a friend with a bomb from the nearby small airfield to clear you of hidden bridge of snipers. Dr7 is gonna love sniping the bridges.
Testing tank combat terrain is a bite. Unlike fighters that just need an airstrip to get into the fight, you have to drive almost very square foot you sculpt for tanks to fight on. And now I have to test every single bridge I lay down to see if it makes any sense where I put it along with balancing helping attackers, defenders and snipers. I still have to test across a diagonal bias of the polygon mesh, I'm betting that will work now with patch5.