For what it's worth, when I interviewed for fall 2009 admission at UNC, I was in the last interview group for December (10 days or so before Christmas), and one of the things Ms. Reid made abundantly clear to us at the end of the day was that we had/were going to miss the last committee review before the new year. She said that even if we knocked the interview out of the park, the earliest we'd get looked at would be the committee's first meeting in Jan (I think she said somewhere around Jan 10th).
So, at least 2 years ago, they definitely didn't meet during break, and if I had to hazard a guess, that probably hasn't changed. Hope that helps a little.