tracking cellphones ?

is it possible yes ! we knew that ( ie the russian firing a missile guided by the cell phone ...)
but are they doind it constantly ?
yes:

Guess who’s tracking you by phone?

By Ben Charny
Special to ZDNet News
February 27, 2002, 3:00 PM PT

The nation's cell phone service providers will soon know exactly where every one of their customers is, at all times, and privacy rights groups are asking what they plan to do with the information.
All U.S. carriers are under Federal Communications Commission orders to make it possible for police to locate cell phones calling 911, something police can't do now. Carriers plan to use the same systems to sell services like helping stranded motorists even if they don't know their location, or finding the closest restaurant.

Because people with cell phone generally always carry their phone with them, the FCC regulations give the thriving market for personal information something its never had a chance to get: the exact locations at all times of more than 140 million people.

full article at : http://zdnet.com.com/2100-1105-846959.html

so next time you drive out of town and come close to a mc drive you'll get a sms saying bigmac's 241 99cents ....