Well, the short answer is, it's difficult and maybe impossible, depending on the actual installation. That's why I asked. I'm not familiar with the wiring on the PS/3 stuff, but for PS/2, the sound files control the functionality of the various functions, and if they're not in the product, you usually don't have that control.
The simple way is to just run them from track power. It may be possible to trigger them from the headlight, but I'm guessing you'd need some electronics as I don't know what kind of power you can draw. You could probably run the firebox from the smoke unit power, that way the firebox would only flicker when you had smoke working. 
