An example of multiple rescue points in Left 4 Dead
The example map isn't complete, it doesn't actually finish the map or teleport, it will just pick one random rescue point in a corner and unlock rescue, if you're playing with bots in Versus as infected, they should go right to it (or just use kill in campaign and the bots will activate the finale and go)
So you can tell which corner was selected, a colored glow prop is placed in the area.
There are two ways of doing it, and I don't know if there's any real difference in the methods, but they are both pretty much the same.
What you do is use point_template's, one for each rescue vehicle. Each point template should contain then name of the appropriate func_nav_attribute for each Rescue Vehicle (The RESCUE_VEHICLE flag should be checked obviously in the func_nav_attribute).
What you don't want is any RESCUE_VEHICLE being baked into the nav or they will go to it every time, that's why you use the point_templates, so you can force WHEN those func_nav_attribute's spawn (so they don't exist during nav_analyze). You can't have any RESCUE_VEHICLE attributes *baked* into your nav/bsp or they will always use the same one every time.
The Offical Dark Carnival Way
multirescue - Example map
You need to run the game with -nav_analyze so it kills the rescue attributes when you analyze, otherwise, won't work, problem is, everytime I add that switch, it crashes on any map load. But if you don't have that issue....
So if you have the same problem as me, just pick your rescue when the trigger_finale is triggered and ForceSpawn the fun_nav_attributes then. Make sure you run the nav_analyze BEFORE you trigger the finale.
The *Other* Way
To generate the nav, follow the instructions below.