TerriK said this already.
When flying on UA for an international trip only, Star Alliance Gold members(50,000 mile flyer) gets into USA Red Carpet Clubs for free. * Alliance Gold + a UA ticket gets you into non USA RCCs no matter what.
Since Centurion gets you US Air 50K status, and US is now part of the * Alliance, Centurion members will be * A Gold. Hence, RCC access for some flights.
Sorry, no UA status that I know of.