After looking at the Sky Watch the Rugby was definately not HD. I thought it was HD because the logo's and scores were in HD and Sky's logo on the top right was in HD but the feed was not?? Im not sure.
Couple of 1024 x 685screenshots here of the same 'live-pause' image. Same camera position, aperture and shutterspeed. One through HDMI (set at 1080i) input other through composite video. Not a huge success taking photos of an LCD screen but the best of a bad bunch. Might try at 720p tomorrow, see if the result is any different.