Because fools would think that using a hostile nation's resources to replace critical infrastructure would be a good idea. The reasoning for this is that the current 911 system has a hard time locating people using cell phones indoors. The proposed solution to the problem is to utilize GLONASS, the Russian version of GPS, to figure out where the distressed person(s) is(are).
Why even mention GLONASS? While it does offer complete coverage of the Earth, so does GPS (something none of its other competitors, can offer), and GPS is unarguably US. And if the FSB cant figure out some use for this information, I have a nice piece of land for sale in Nye County, Nevada.