I have used them in Colorado ( back in the late 90's early 00's) but it was only to ride from camp to a trailhead, or to a particular basin and then walk in from there. I never hunted from them per se. Very seldom did I every ride mine in daylight.
Now I have never seen it personally, but an elk hunter I have shared an elk camp who has taken more elk than I will ever dream of taking has told me numerous times of where he was working a bull ( or two) during the peak rut. All of a sudden they shut up. A few minutes go buy and here comes a hunter riding a wheeler. Parks within a few hundred yards of where my friend is and starts blowing bugles and cow calls. Silence. Wheeler starts back up and once it gets out of earshot the bulls start screaming again. That story has stuck with me ever since he told me. One of those times 10 minutes after the machine left, he arrowed his biggest bull to date, a 378 that shut up while the wheeler approached and took off.
They don't get big by being stupid.