The Blue Box Podcast Episode 247 interviews Dylan Rees, author of "Downtime-- The Lost Years of Doctor Who", who has this to say about Kaldor City:
"Kaldor City is an audio series, by a company called Magic Bullet,
which is set in the world of Chris Boucher’s Doctor Who... so it
involves “The Robots of Death” Commander Uvanov, a character called
Kaston Iago played by Paul Darrow, it's got Carnell from an episode of
Blake’s 7 and it almost sounds like, what we’d call now, the ultimate
fanwank, but it is one of the best things to be made related to the
Doctor Who universe.
It’s funny, it’s action packed, it’s a gripping six
CD story... it’s an incredible production, and I’d never hear it until I
did this book, and I wasn’t even going to cover it. I was like, “I’m
sure they did like two CDs and that was it..” and then all of a sudden I
found it and I was blown away.
So my one recommendation out of anything that comes out of this book is
that you have to find Kaldor City and their follow up Faction Paradox."
You can hear the whole thing at this link (the quoted section starts at 1.05.30).