I think most games abroad are beamed back using the respective countries pictures, which probably explains the reason you see a streaker or protester running about, or violence in the crowd. Over here the cameras tend to turn away from any problem or spectacle that arises.
mostly they just use footage from existing cameras but for live matches and extended highlights extra cameras are generally brought in by the tv people to gain better coverage, this is my observation from being at matches anyway, a live sky match equals way more cameras