That is very easy to do with O31 switches and tubular. I am unfamiliar with fastrack, however, if there are three wires connected to the motor for the activator/controller, then all you need to do is this:

Hook up a single controller to the switch, next, run two wires to the next switch. These wires attach to the outside conection posts on the first switch. Whe you connect the wires to the second switch, the connection is to the opposite connection post. One switch controller activates two switches and the switches should switch trains from one loop to other automatically.