Public safety agencies in the US have been pushing for some time to have the so-called 'D Block' portion of the 700MHz wireless spectrum all to themselves, and it looks like they can now officially count on the support of the White House in that effort. The Obama administration announced today that it's backing plans to reserve the airwaves -- estimated to be worth $3 billion if they were auctioned off -- for a new national public safety network, and it also plans to ask Congress to approve the additional spending needed to actually build out th