Michael Moorcock's having recently written a Doctor Who novel would probably be another exception.
The Moorcock book came about in a strange way. A distributor approached BBC Books and said, "There are all these famous authors who talk about how much they love Doctor Who
, so why don't you publish a book by a famous author because it would have all sorts of marketable hooks in the book market?" BBC Books thought this was interesting, they approached Moorcock, he was game, and that's how The Coming of the Terraphiles
came to be.
Since then, we've had Doctor Who
novels by Jenny Colgan, Stephen Baxter, and (though actually written by Gareth Roberts) Douglas Adams, with a book by Alistair Reynolds on the way. (I'm discounting Dan Abnett's The Silent Stars Go By
, because the sales kit on that book promoted it as a "the first Doctor Who
Christmas novel," which was the angle BBC Books wanted to take with it.)
Interestingly, this got BBC Books what they wanted -- an American publisher. Ace Books picked up Roberts' Shada
and Baxter's The Wheel of Ice
for publication in North America. (I presume they're going to pick up Reynolds book as well.) This is something BBC Books has wanted since the mid-90s, someone to publish and distribute the books in North America rather than have to deal with an importer (which was a constant source of frustration for them even as late as a decade ago).