It can get to -30 deg Celsius or a tad lower for brief periods; this would most often be an overnight low, maybe a couple of times through the winter, sometimes a bit more prolonged. The elevation in my area is about 1130 meters. Due to proximity to the Rockies, we get chinook winds through the winter - warm winds that melt the snow, exposing the soil during the winter.
People all across the prairie provinces (in places where it gets a heck of a lot colder than this) grow sempervivums as regular border plants. So, yes, very hardy and not even requiring rock garden conditions - though they certainly look their best tucked into stonework and filling the gaps between rocks, as they grow in nature.
As with most alpine plants (and an awful lot of regular perennials), the thing to watch out for is winter wet.
