The FGT blog offers a detailed entry named How The FCC Plans To Destroy GPS – A Simple Explanation.
From the entry: " [...] the FCC has given conditional approval to LightSquared’s 4G LTE proposal. If implemented as planned, all current GPS receivers will no longer operate correctly in areas covered by their system, which include the overwhelming majority of the US population. [...] This GPS interference isn’t just a hypothesis. Members of the US GPS Industry Council, Trimble and Garmin met with the FCC on January 19th to present and discuss Garmin’s tests of the LightSquared proposal, and its potential for interference with GPS receivers. [...] And yet, on January 26th, waiving many of their standard procedures, the FCC gave conditional approval to LightSquared’s proposal. The only bone thrown to the GPS community was the requirement that LightSquared work with the GPS community to resolve these interference issues. But since LightSquared is funding the study, there are concerns about how unbiased the results will be. Unless you can change the laws of physics, and principles of electrical engineering, you can’t resolve this problem directly with existing GPS equipment as-is."
But if LightSquared does cooperate and don't mess with GPS signal, then this may become a non-issue.