Although a valid concern, in practice it really doesn't seem to be much of a problem with these engines. Worse case scenario would be your throttle sticking because of a frosty slide, the kill switch or choke would still kill the engine & coupla throttle twists should free it up in any case. It's a LOT easier to pull over for a sec on a bike than a plane lol
Carb icing usually has far more to do with ambient humidity than temperature, but even still I've never had a problem with it w/these lil carbys. Another difference is it's not uncommon for an airplane to remain at the same throttle setting for prolonged periods (allowing ice to build), whereas that's highly unlikely w/the bikes.
Here's a buncha info on both carb ice and the effects of ethanol if yer curious;
AOPA Combating Carb Ice
Boatbuilding.net | Pros and Cons of 10% Ethanol in Gas