>I assume that they must have a lookup database based on the browser identifier for is cookies is supported. It would be an interesting test to see if turning of cookies in the browser made the cookies return false.
>

There is such a database. Its called BrowserCaps in your machine.config.

It knows if the browser supports cookies (cookies=true|false in machine.config) but not if they are disabled. For that you need some javascript or http://www.browserhawk.com/