There's some headway being made as to have this working in tvheadend without needing to relay the whole stream.
Cheers.
https://github.com/tvheadend/tvheadend/commit/45ae4fb70c81f1a7159931b08bf3a415d7873307
I started working on adding powervu implementation on tvh, but haven't had much free time. Maybe after the summer I will have some time, if nobody else does it first...