Ostensibly yes, though I suppose it depends on the make/model of the laptop and webcam. Someone with pretty solid reversing skills would need to figure it out for that specific laptop or line or laptops.

I've read that it can be possible on some makes and models although most of them employ a system where when the camera is active then electricity passes to it, it passes through the LED first so to even reach the camera the LED has to be illuminated therefore making it not possible.

Yes, of course!