This time, UK viewers aren't so lucky: The Plan is not on DVD release here yet, and I don't think Sky have set a date for airing it yet, so it probably won't happen until they do.
But is it any good? An interesting diversion, but not essential, I'd say. NOTE: there are some spoilers below if you haven't seen the rest of the series...
There are two really good things about The Plan. One is some of the best CGI (for the destruction of the colonies) that the series has ever had. The other is Dean Stockwell getting a lot of screen time and being superb, in a his inimitable Dean Stockwell kind of way. The third thing of note is that there is an interesting subplot involving a number 4 Cylon (the "Simon" character - Rick Worthy), which is nothing mega-exciting but nice, in that number 4 was kind of underused in the series in general.
There ain't much else, really - director Eddie Olmos (Adama) did about as good a job as he could cutting between footage from the miniseries and Series 1 and 2, and new footage shot to 'extend' certain scenes, but it's not easy when you're joining together 2009 footage with 2003 footage. How many of us look exactly the same as we did six years ago?
So the whole thing was nice, but a bit 'join-the-dots' - an exercise in weaving in as much backstory and parallel story as possible with the confines of a narrative that had already been pretty thickly sketched. And there are some key personnel absences which make the whole thing less convincing than it could be - for example, given that we know that there was at least one number 3 agent (Lucy Lawless) in the fleet (see series 2 episode "Final Cut"), isn't her absence from the Cavill "briefings" in the chapel a bit strange? I know it was because they couldn't get her back to be in The Plan but it's still a bit inconsistent.
Oh well - given the constraints they were under, it's not a bad effort. But probably for completists only (which of course, is a group I fall into).