Last year his agency CV stated that he was working on a script for a Doctor Who movie. The credit quickly disappeared once it was noticed. So, I'd say that Russell wrote a script to shop around to get interest in the project. Now that Yates is on board he obviously wants to develop his own script.
If RTD did write a script for a BBC Worldwide
Doctor Who movie, you can be assured that he didn't do it on spec (writers don't work on spec in Hollywood) Whatever he was paid will be applied to the development costs of Yates' film. (This is why
Superman Returns had an astronomical budget; the film absorbed the costs of a decade's worth of false starts.) Assuming a treatment and first draft, RTD would have been paid between (roughly) 50k and 90k for a script that won't be used.