IF the ultimate objective is TMCC control of TT operations, I'm imagining using using the Front and Rear coupler controls on an engine-board or TMCC-controllable auxiliary board (e.g., Electric RR module) to drive a solenoid locking pin. For example, fire the Front coupler to engage the lock, fire the Rear coupler to disengage the lock.
Or, for $5-10 in eBay modules, you could cobble together an RF-wireless control (to eliminate the slip-ring wiring problem) where you'd use the track AC voltage, convert to DC+ to lock, or DC- to unlock. Hard for me to gauge what's in your comfort zone as far as wiring, soldering, messing with electronic modules...