isn't it Alaska where mode S is making life a lot easier
Well actually not quite. ADS-B just requires a datalink. The FAA has introduced plans for ADS-B using both the "Mode S extended squitter" (i.e. let's shove some more bits into a Mode S reply) and the Universal Access Transceiver, which is a low cost datalink designed for aircraft that don't need Mode S for other purposes. The Capstone (Alaska) trial ADS-B is based on UAT, not mode S.
http://www.alaska.faa.gov/capstone/avionics.htm