This is a cut and paste from the above site...
Antenna Module and Cover
The radio antenna, instead of being imbedded in glass, is mounted under the roof. This is a huge antenna, spanning the width of the vehicle. It can be removed from inside the vehicle after removing part of the headliner (see Figure 4). The antenna module can also be a global positioning system receiver and traffic message channel receiver, depending on the vehicle options.
The antenna module is not open to the sky on top, but covered with a thermoset epoxy cover. The antenna module cover is attached with stationary glass urethane.