The GPS bracelets, here anyway, are for home detention, and this guy's home is in Germany, so that's a problematic argument.
Detroit is pretty close to Canada, and there wouldn't be much to stop him from crossing that border.
My WAG was that they were going to hold this guy to squeeze him and flip him, but it seems more plausible that they flipped him back in Germany, and we are watching his social cover for ratting out the others. It doesn't make much sense that he came to the U.S. for vacation when he could be facing 169 years in jail - unless he already had a deal made, or that his lawyer tipped off the feds to arrest him. The dramatic last second arrest getting on the plane, and holding him without bond is part of the cover show. We have yet to see the traditional perp walk by the feds of the disgraced big shot, I might add.
It will be interesting to watch the show. It looks unseemly that VW is the one to get the book thrown at it when so much white collar crime, in the private sector and government, has been virtually ignored for criminal prosecution, but I guess you have to start somewhwere.