Not very well.

When it gets cold enough, the water in the ground freezes and expands and basically "squeezes" the fiber. The "1"'s, which are long and skinny, can still slide right through the fiber but the fatter and wider "0"'s sometimes get stuck. This causes the fiber (Internet pipe) to get clogged and, eventually, stopped up completely, similar to how car crashes on the Interstate can quickly bring vehicular traffic to a standstill.

(Source: I was the Senior Network Engineer for a FTTH ISP, until just recently.)

I'm sure Google Fiber works fine in cold weather, but fiber optic cables buried in city roads in a two inch trench covered with a flexible rubber gasket have demonstrably poor resiliency to snow, ice, salt trucks and freezing temperatures.

I'm in Kansas City and have Google Fiber. I don't really know how cold Louisville can get but I can tell you that we got pretty gosh darn cold (10-20 degrees below 0F) last week during the Polar Vortex freeze. And we're going to be flirting with those temps again this week. But to answer your question, I have not noticed any disruption or degradation of my service as a result of the cold temperatures.

EDIT: As others have said, I think the problems in Louisville come more from shoddy installations thus making them more susceptible to extreme weather rather than 'fiber not working in cold weather'.