Tenth Doctor Adventures Volume 3

My understanding (can't remember from where, this is definitely hearsay) is that Freema felt a bit mistreated by the producers; she'd been contracted to do two series of Doctor Who but the fan reaction to Rose's follow-up wasn't great simply due to Martha's position as the "rebound girl." So the producers decided to replace her with Catherine Tate. Yet they still had her under contract so rather than let her find other work right off leaving Doctor Who, they pulled her in for guest-appearances throughout Donna's season, as well as those three Torchwood episodes which were actually centered on Owen anyways, giving him all the juicy material any actor would love to sink their teeth into, while Freema's material was to provide exposition and moral support. Which must be frustrating for any actor, especially if they're just itching to make the most of their Who-heightened profile in landing new roles.

Then they had thoughts of having her join Torchwood as a main cast member, but by this point her experiences with the franchise were leaning in a negative direction, so the most she agreed to was cameo-ing in David Tennant's finale.

But... this is all unconfirmed, of course; I'm just a know-nothing fan like anyone else. To me, though, this would explain Freema's reluctance to rejoin the franchise for audio-plays.

I wonder what might happen if David Tennant reached out to her and made a good case? They seemed to get along well in behind-the-scenes footage and she showed up for his finale, but who knows?

But all my speculation aside, it's fully possible she's simply too busy with bigger projects to schedule in radio-plays right now, but might find time later in her career?