As with all winter tyres, they should be used during the winter season. They are designed to work during cold temperatures and for the conditions that prevail during this season. The non-studded tyre, which is sometimes referred to as friction tyre, is a tyre that will perform well on any winter surface. If you get a set of high quality non-studded tyres, they will perform as well as studded tyres.
The high quality non-studded tyres have advanced a lot during the last 10 years, with a lot of new developments that give them excellent traction even on icy surfaces. On snow, unless it is tightly packed, the non-studded and the studded tyres have always performed quite equally. The big difference has been on ice. The new non-studded tyres that are of high quality are made of a special rubber compound. This will give them sufficient traction when you accelerate and brake on ice. There is also other revolutionary design modifications in the tread, that act like claws that can grip the ice. So no, regardless of what winter surface that you will drive on, you can drive safely with a non-studded tyre.