LC+ Steamers turn the smoke off totally when stopped, I checked when I got my Camelback. I'm pretty sure the others do as well. It would have been cool for them to have idle smoke like the diesels, but nooooooo.
The low pulse from the LC chuff opto would work fine for my Super-Chuffer as long as the signal didn't mind the 4.7K pullup and the .1uf cap that is across the chuff input to prevent spikes from hitting it. Actually, there's a 100 ohm resistor, the .1uf capacitor, and the 4.7k PUP in the circuit to the input port.