This is because, as of Friday, it's wrapped. Everything that's going to be shot has been shot, except for the chorus of Ghosts (Rupert Everett, Mark Heap, Julian Rhind-Tutt, Noel Fielding and David Walliams as Secundus, Tertius, Quartus, Quintus and Sextus respectively, along with the briefly dead Primus, Jason Flemyng, and Septimus, Mark Strong) who get shot against green screen in September.
I think we'll find out when people go in tomorrow how much dust and ash is around, whether it's damaged costumes and so on, but we're okay -- and Casino Royale had wrapped as well.
(The 007 stage last burned down back in 1984, with LEGEND. So two major fires with no loss of life...)
Miss Holly Gaiman makes a special guest appearance (as does the 007 stage) in Moriarty's set visit report -- http://www.aint-it-cool-news.com/display.cgi?id=23960 this is the second of two.
And here's a photo of the door to the 007 set, the last time I passed it, a few weeks ago. They'd left it open, and there weren't any security guards about, but it seemed much more fun to take the photo of the door than to go inside and snap away...