Although Sprint has coughed up some $1 billion over the past few years in order to nix the interference between 2,200 public safety agencies across the US and its iDEN network, it apparently hasn't done enough. Reportedly, the FCC has warned Sprint that it "could lose access to the signal spectrum used by its Nextel- and Boost Mobile-branded wireless services" if it doesn't remedy the problem by June of 2008. Supposedly, Sprint is "working hard" to settle the issue, but it's not wasting any time asking the US Court of Appeals to get involved. The carrier claims that these shut down threats could force it to halt signups of Nextel-branded customers, and furthermore, around three million public-safety workers would purportedly lose service if the FCC did indeed shut down the Nextel network. 'Course, industry analysts are suggesting that regulators wouldn't really go through with shutting it down, but if nothing else, this should light a fire under Sprint to expedite the process.