I remember reading an article about the D3 when it came out and a bunch of photogs used it at a Packers game in Greenbay....problem? Batteries. The temp was around zero and batteries were failing within 15-20 minutes, but the cameras performed just fine.
My ancient D200 - I shot it in Colorado at altitudes over 12000 feet in sub- freezing temperatures and just kept a spare, warm battery nearby. No issues.
D600 - it should have no problems, just keep a spare battery or two in you pocket next to your body and swap as needed.
"Extraordinary claims require extraordinary proof " - Carl Sagan