Doctor Who Christmas Special plot details

Via Outpost Gallifrey, the BBC have released their Christmas 2005 TV highlights press release. It includes a detailed description of the episodes setup (so don't read it if you don't want to see spoilers!). Doctor Who is the first show mentioned in the release, so the BBC obviously see it as their big hitter. (Who would have thought it, a SF show the BBC's top Christmas offering?)

Also worth noting is that BBC3 is down to show Doctor Who. Whether this is just a repeat of the special or last series repeated (again) is not mentioned.