In “this”:http://www.defenselink.mil/news/Apr2006/20060406_4741.html DefenseLINK press release DoD assistant secretary Peter C.W. Flory assesses the US BMD(Ballistic Missile Defense) system as having reached initial operating capability. He says it’s still primarily in testing mode, but he apparently believes its stable and reliable enough to handle incoming threats. Whether this means it’s actually “live” and online is unclear, although the open-ended technical nature of the system means that new components will be phased in as they become operational rather than trying to deploy a complete system at the flip of a switch. For this reason as well as for strategic considerations we’re unlikely to see a formal announcement.
Much more information on the system is available from the “Missile Defense Agency”:http://www.mda.mil/. I ‘d also like to try to research and compile a quick summary of BMD technology sometime soon to post here.