They do not even need the large stations to do this anymore. There are several variations of mobile systems that can fit in a van allowing them to sit across the street from you and monitor your computer and all other devices you own. I do not mean by bugging your devices or using distance hearing devices, I mean by monitoring the actual electro magnetic output of the devices.
Here are a couple links
http://www.wired.com/news/politics/0...2097%2C00.html
http://cryptome.org/nt1-92-1-5.htm