No. If you have a vacation that spans over your use year month, then you must use points from two separate use years.
With a December UY, if you wanted to make a vacation for example Nov 26 - Dec 2nd, you would have to use 2005 points for Nov 26-Nov 30, and use 2006 points for the Dec 1-Dec 2 dates.
You could not use any of your 2004 points that you banked into 2005 for any of the December days.