That article is very misleading.  For one, when it says “A typical guard band between spectrum users is about 2MHz.” it fails to say under what conditions.  Guard bands very across the radio spectrum and depending upon the signal being transmitted.  At 146 Mhz, for example, allocations are normally spaced with 0.015 Mhz between them to accomodate how wide the normal signals are there. As you get higher in the spectrum, signals tend to take up more bandwidth on either side of the specified frequency.  The fact that they take up more space than the specified frequency is true of all radio signals.  The lightsquared signal is described as being “broadband”.  As a radio person, to me that says it’s signal is very wide and at that high of a specified frequency it isn’t surprising to me that it would exceed a 2Mhz guard band, especially if it’s using a spread spectrum modulation.  The 23 Mhz guard is simply meant to make sure that the signals that lightsquared is transmitting don’t extend into the GPS frequency range.

BTW, while the political arm of the FCC does things I think are fairly questionable, it’s technical arm is top notch and has a long history of technical excellence.