I made a small demo, learn from it, it's pretty simple and easy to understand. The basic idea is to check for the distance between each camera and player, and if player is near one, trace from it to player, if trace doesn't hit anything, we attach camera to it (to the placed camera model from WED). Also, you can see in the demo sligtly visible wall, it's passable for player, but not for the camera traces, so you can place walls like that in your level, to have more controll over the cameras.
download link Best regards!
