Some packet sniffing prompted by you revealed the following:
MRV transfers can be initiated from a PC very similar to TTG transfer but with the addition of video format specification at the end. For example:
Note the format specification at the end: &Format=video%2Fx-tivo-raw-tts
While this is all well and good and avoids having the Tivo have to re-mux and re-encrypt and hence speeds up transfers to MRV speeds, the question is what can be done with the resulting encrypted transport stream file on the PC?