MattM provide this interesting news item to me today.
It is an interesting read.
However given the options to hide the path your packets take that are available to most ISPs today I would be surprised if they would make this monitoring so noticeable. Simply tracerouting to see if you packets go through sffca.ip.att.net is too simple of a detection method.
For more details see the link.

The Newbie's Guide to Detecting the NSA
http://radar.oreilly.com/archives/2006/06/the_newbies_guide_to_detecting.html