I believe some of the plug-in modules (lamplinc) still have a load "sense". Such devices can detect when the device plugged in is manually turned ON or OFF. When sensed, I believe the modules will, themselves, turn ON or OFF. The original outletlinc had that same feature, but I do not believe the current generation has it. Of course, if the device plugged into the lamplinc is left OFF manually by one of your guests, it cannot be turned on by insteon. Another problem is that the sense feature is via a small electrical current. For low-power loads, such as LED christmas lights, this current is enough to cause the lights to appear to be on (if dimmed).
Also keep in mind, this is different than the "sense" line of the micromodule. I don't think this sense wire would help with plug-in devices such as a lamp.