I have 3 parallel tracks with Lionel Fastrack crossing gates on the outside tracks. I would like both crossing gates to open and close whenever a train is on any of the tracks. I am using the isolated and insulated tracks on each side of the gates.
Have you tried the Lionel IR detector…it uses either track power or supplied power, looks like a large signal battery box… you might be able to adjust the sensor to span the 3 tracks. Wiring is a minimum and cost for the detectors is resonable.
Assuming that your outside rails are common among the three tracks, just connect your insulated control rails together, then use them to operate the crossing gates.
That is the same way I do it and I can’t see why it wouldn’t work with fasttrack.