There is the DVB specifications but mpegII encoding can literally be set at any bitrate which would be dependent upon how much each individual channel wishes to pay for transponder capacity (Satellite) and how what other services they wanted to offer on DTT.
You've also got to consider that many broadcasters use statistical multiplexing which takes a handful of channels and shares the available bandwidth between them so there is no "set" bitrate.
The bit-rate is variable as almost all channels and multiplexes use statistical muxing.
If you want some averages, I have a "special" satellite TV card & PC s/ware that reads the raw MPEG TS (Transport Stream) ; I can tune to a transponder and see the instantaneous individual data-rates for every channel in a multiplex along with all other PSI info (program specific information).
The software is specific to the Twinhan VP-1020 PCI satellite cards and is not in the public domain (written by a British friend of mine who now lives in the USA).
You would have to tell me the actual frequencies of the transponders containing the channels you want me to check (not the channel number that you use for the $ky digibox).
They should be listed on Lyngsat (www.lyngsat.com).
Chris Muriel, Manchester - author of Digital SDatellite FAQ.