So is your 4-LED module for sale?
I'd also think if your module can operate on track AC...it could also operate from a PS/2 pulsed DC output? In other words if powered by a PS/2 light output it could turn on when the engine electronics starts up rather than whenever it is on the track (if connected directly to track AC).
OTOH, the firebox had to be fueled and flickering hours before any engine operations...