Therefore, its known narrative elements are not a part of the Doctor Who universe. It may have been the basis for a similar story in another medium, however — and that story may indeed be a part of the DWU.
The Hollows of Time was the fifth episode of the planned original season 23. It was planned to be written by Christopher H. Bidmead and directed by Matthew Robinson. It was later adapted into a Big Finish Productions audio play. It was also going to be the return of the Tractators.