BMW hold these cladestine evaluations all the time either at the Museum or The BMW Welt. Or within the FIZ.
Of course they throw the public out before hand. But the museum gets used a lot too. I remember a new vehicle presentation in the ground floor of the museum in which the Roadsters which were normally on display were parked in to the corners, so this upcoming vehicle family could be accomodated.
The Museum recently hosted an evaluation for future Rolls-Royce models.
The Welt, a couple of months ago just before the BMW i8 Spyder went to China for Beijing played host to an internal drive on the main delivery floor of the BMW Welt that meant driving the car around the delivery track to our hearts content.