Did the cold front cause usability issues with the batteries in electric cars?
Telsa Owner's Manual, page 83


  "Temperature limits:
  Do not expose Model S to ambient temperatures above 140F (60C) or below -22F (-30C) for more than 24 hours at a time."


It's an explicit warning from the manufacturer, who knows that the batteries and electronics will be affected in sub zero weather.  So yes, they are affected.

Of course, batteries in use will experience self heating, so they will not be exposed to the same temperature as ambient weather, so should not see as much as a performance hit as inactive batteries.