http://velonews.competitor.com/2010/04/bikes-and-tech/technical-faq/technical-faq-carbon-in-cold-conditions_111530 summarises to "No problems"
CF (carbon fibre) components are used extensively in launch/reentry
vehicles and satellites where the temperatures range from superheated
to near absolute zero. The ultra low CTE (Coefficient of Thermal
Expansion) of carbon fibre make it ideal for these temperature
extremes. I find it very hard to believe that a bicycle sustained
damage during winter storage in a cold garage – regardless of the
earthly location. I have seen “green” (not fully cured) paints and top
coats crack in extreme temperature conditions but never a CF composite
Although if your bike had water in it and that froze, you would have a different problem. To deal with this, dry your bike, and hang your bike so it drains - often there are two breather/drainholes at the aft end of the chainstays... but do eyeball them first.