Changes the recipes of BBR to depend on rails to be more in line with modded rail recipes. You can also enable more expensive recipes via mod settings.
The stone in the rail recipe gets replaced by the bridge material (wood, iron plate or stone brick).
So if your modded rail costs 1x stone, 1x steel and 1x turret (don't ask why), with a cost multiplier of 1, wooden bridge rail will cost 1x wood, 1x steel and 1x turret. With a cost multiplier of 5, wooden bridge rail will cost 5x wood, 1x steel and 1x turret.