I'll try to get around to testing it this weekend - had totally forgotten about this thread. I have a '01 Polo which I'm fairly sure has a PWM illumination wire, as I have to turn the illumination full up or down to get stable behavior from the buttons (otherwise they blink bright/dim with about 1/2 Hz frequency)
Unfortunately we have mandatory dipped beam (often with reduced intensity) even during daylight, so the illumination wire is always active with the car on.
I've been thinking of tapping into the headlight switch (auto/park/on) for a "proper" illumination wire, but haven't yet been annoyed enough...

/Michael