I don't know the source, but it seems techincally fairly thorough and well developed, so possibly from within the industry or SRA» /DfT» .
Looking at it quickly, it seems to provide a clockface service pattern in the Bristol area, with some extra peak trains. I assume the trains which show numbers next to both diagram 1 and 2 at the top are double length trains. I don't know to what extent this timetable would meet demand, whether it is operationally feasible, nor whether it would be good value for money.
Here is a link to the background work.
http://www.dft.gov.uk/foi/responses/2006/september06/swindonwestburytrainsservice/bristolroute