As someone pointed out in the comments to the original Radio Times article, that would be a really
surprising Doctor Who Confidential
, since the show was cancelled two years ago. But of course they could do a one-off announcement documentary if they wanted to.
Doctor Who Magazine
reported a few months ago that there would be no classic Doctors in the special. Of course, it's possible that plans have changed since then, or that they were fibbing so that a two-minute Paul McGann cameo will feel like a thrill rather than the least possible classic series involvement.