Lol i was goign out the daily parking exit at Dulles back in august or so and found the cell phone area by accident. To get to it you ahve to be going out the daily parking exit, incurring a fee. Then you have to get back to the terminal.
I guess it makes sense, since it takes the same amount of time to get the the terminal from the parking area as it does to get off plane, get baggage, and leave.
On a side note, it appears that there is indeed a metro station at dulles! The large concrete "thing" at the front of the hourly lot right in front of the terminal could be an elevator shaft. Who can urbex it for us?
http://www.clouse.org/metro.html#Dulles_Airport_Rail