Probably NPS could offer this if they chose to do so.
You know right after I answered his question, I totally forgot - NPS DOES uplink another station that is NOT considered a grandfathered superstation. They uplink KTVD-MYTV out of Denver, as well as PBS stations KRMA & KBDI in their Denver 8 network package.
I have always wondered how NPS is getting by with this, but since ONLY 4DTV C-band customers can sub to them, nobody probably notices that should...