If, as the specs say, they are 24 bit AD, 24 bit processing and mixing and 24 bit DA then I suspect the .VR8's are 24 bit? Then maybe they are only converted down to 16 bit when output as a .wav or on the cd?
Well I have managed to answer my own question by successfully importing a BR1600 .VR8 file into Audacity as a raw file import. It imports successfully as a signed, 16 bit pcm, little-endian, 44.1kHz file. Imported at 24 bit, it was a massively clipped, payable but unlistenable mess.
So now I know for sure. It is storing the audio data at 16 bit. I can understand the 24 bit delta sigma AD oversampling but I have no idea what they are refering to in the specs in regards to 24 bit processing / mixing / DA unless they are only talking about the BR1600 being used as a mixer and not as a recording device and are just trying to impress us with it's pseudo 24 bit credentials.