As someone who loves driving and exposing ecomyths in about equal measure, this is a story I just loved.
So not only is the Prius ugly, it is not the ultimate in frugal, fuel efficiency it claims. To really make the comparison even, the driver of the Prius could have turned on the air conditioner and the stereo (as most of us would for a 500 mile journey across Europe) and the gap between the BMW and the Prius would have been even more severe.
Reminds of the analysis I posted some time back which showed a Hummer was more environmentally friendly than a Prius. Sometimes truth is stranger than fiction, or just plain inconvenient.