There does seem to be a small grace peroid at least for A-List and A-List preferred. I have flown on January 1 and 2 and recieved A-List benefits which were more than I was technically entitled to. I'm not sure how it works. I think it may be when your boarding position is assigned before the end of the year. The same thing may apply to CP. I'm pretty sure January 3 is too late.

I'd be interested in other's experiances.