Hey Trent, first of all SFMBE. did you found any solution yet?
i played single player mostly, so i editing RULESMD.ini a lot. if you want indestructible bridge (almost), try this;
1. open RULESMD.ini
2. find BridgeStrength=1500
3. edit the amount (smaller means more easily destroyed), i edited to 999999999
Hope it helps.
"What a view!" - Amphibious Transport