So, in this week's Radio Times (UK tv listings for the week - very highly connected with the BBC), not only do they have the big Billie Piper interview (her original name was Leian Paul Piper, btw), but the listing for the Doctor Who Confidental gives something major away.
"12/13. New. Behind the scenes as Captain Jack and his Torchwood associates return."
Sunday's repeat is described more simply:
The return of Captain Jack.
Of course, you can consider that maybe someone has got the new Torchwood series mixed up with this Torchwood appearence in Doctor Who, but still.... And considering the possibilities for a certain old enemy of the Doctor also returning based on that one particular death in the next week trailer....
Army of Ghosts might well turn out to be full of surprises.