
It is pretty simple - If a turret is actively tracking or shooting an enemy, it produces a circuit network signal (configurable) when connected to the circuit network.
Also, if a turret is damaged, it produces a different signal (this could be a value related to how damaged it is).
Why could this be useful?
Well you could hook it up to a lighting system which warns you when an attack is going on and sends a train down to resupply it.
But finally, my favourite reason is to send trains out to run over the attackers whenever the turrets are engaged, just like in the trailer!

I'm sure there are plenty of other uses or variations on this idea - feel free to discuss them
