Wikipedia says different:

"Cat's eyes are particularly valuable in fog and are largely resistant to damage from snow ploughs."

http://en.wikipedia.org/wiki/Cat%27s_eye_(road)

As does the Reflecting Roadstud's manufacturer's website:

"The final component part of the “Catseye” is the cast iron base. Manufactured from Grey Iron, the cast iron base affords excellent protection to the rubber insert and has been specifically designed to withstand the demands of heavy traffic and effects of snow-ploughing."

http://www.percyshawcatseyes.com/products/the-cats-eyes-road...

The cat's eye will lift the plow off the ground and at that point the plow won't be doing its job. Not much snow in the UK.

Catseyes are a menace for bicycles so this would be great in urban areas, and especially dedicated bike tracks, eliminating the need for lighting.