Ok I found the info on the beeb's site by Rupert Brun, Head of TEchnology for BBC Audio and Music - slightly abridged:
For Radio 3 live broadcasts are carried as 48kHz linear encoded digital signals. They are down sampled to meet the requirements of the Continuity Desk system which uses 44.1kHz. At this point the format is carried as BWAV (broadcast WAV) streams. This is also where media is streamed from ripped CD's etc. (hence the 44.1kHz sample rate. This Continuity Desk system then feeds the signal to the 'Broadcast Router' that splits the signal into the broadcast chains including Terrestrial and Satellite TV, DAB and VHF FM audio - but at this point the signal is then up sampled back to 48kHz (The BBC acknowledge this is not optimal and hope to maintain at 48kHz with a new play out system some time in 2012). The VHF FM (compressed using an Optimod processor - thanks Noogle) and is low pass filtered at around 15kHz ready for stereo multiplexing and distribution via NICAM. The digital feed for all radio stations other than Radio 3 go through extensive processing and compression suitable for their medium. However Radio 3 is not processed or compressed for any digital platform.
The internet radio for non radio 3 shares the same processing as DTV.
The 48kHz data feed is AGAIN resampled to 44.1kHz and then fed to the Coyopa system, which is the BBC's streaming platform.
The linear digital signal is then shaped to -4dBFS to account for encoder over shoots and then fed to the Fraunhofer encoders which outputs AAC-LC. The codecs and attenuation on the Coyopa system is exactly the same for all web radio stations with the bandwidth being the only variable with Radio 3 using 320kbps AAC-LC.