artifacts in NTSC NFL on CBS

IIRC CBS films their NFL broadcasts in HDTV (720p?). When I watch games on my 27" NTSC GAOO I can see alot of artifacts, mostly jaggies & edge ringing (especially in play shots). Does anyone know if these are due to the HDTV downconversion or some sort of pre or post compression?

On of my questions/concerns is when only HDTV what the downconverted NTSC picture will look like.