I just did a quick experiment with my Sunfire ultimate receiver. I have a Satellite PVR connected to the TV via HDMI and an optical cable to the sunfire. I also have the TV optical out connected to the sunfire.
Now, first I played a movie on the PVR. with the sunfire input set to receive the digital signal from the PVR the sound is 5.1. (sunfire has two blue lights to indicate processing; one confirms a digital signal and the other confirms DD. My ear confirms 5.1. Now, I switch to the sunfire input that receives the TV optical input and low and beyhold, the DD light goes out and the sound is now only 2CH.
Next, I fire up Netflix which is received by the TV directly from my wireless router. I leave the sunfire set to receive the optical signal from the TV. I fire up the next episode of Breaking Bad and the DD indicator on the sunfire lights up and again the sound is 5.1
SO, it seems that the TV optical out is capable of sending a DD signal (when it originates from the TV) however, it does not seem to "pass through" a DD when it originates from the PVR.
I don't know if this helps, but that's the way the sunfire works. It just automatically plays the DD or 2CH w/o me having to select anything.