I did a bit more research with the book Video Demystified, fourth edition.
On page 75, under SDTV YPbPr Interface, it says that the recievers should be AC-coupled.
Here is a pic from page 76
The numbers on the left are the voltage levels. So as Ali Chen mentioned, the PbPr signal is indeed 700mv pk-pk, but here it listed as 0.3-1v, and the Y is 700mv for the luma, and another 300mv for sync.
Now, I would guess that, since the the receiver is AC coupled, The PbPr can pass as 0-0.7v from the transmitter, because it is riding on DC, which will filter out to +-350 mv. For the Y, I have to shave off 300mv from one of the ends, and I can't shave off the sync, so it looks like I would have to sacrifice some brightness.
I have not tested this out yet, so I have no hard results. This is all in my head.
I would love to hear what others have to say about my understanding...