I know it is a bit confusing, but what it think you are asking is can you be recording 2 HD programs on one PVR, and a second PVR is recording a SD channel, and still be able to watch PVR recorded TV. The answer is YES you can do that.
When Whole Home PVR came out here is what I did to test it. (I have 4 TV's, but only needed 3 to test this.)
TV1 - The VIP1216. - Setup to record 3 programs simultaneously (475 - TSN HD, 422 - CTV HD, 104 Discovery SD) + I then accessed my PVR and turned on a HD movie I had previously recorded. - so one TV was recording 3 shows and watching back a single HD show.
TV2 - tried to tune to a live channel - I got a conflict screen - all streams in use, I then turned the TV to channel 104, and was able to watch it as it was a live stream already in use. Then went to PVR, and turned on a different HD movie I had previously recorded (different than the one already on TV1)
TV3 - Did the same thing as TV2, - got conflict on a new live stream, but able to watch an already live program (475, 422, or 104). and was able to watch back a 3rd HD show from the PVR.
So on 3 TV's I had 3 live programs recording (2HD, 1SD) and watched 3 different HD programs from the PVR all at the same time. Total of 6 programs all on at once 5HD and 1 SD.
Hope this helps