Ultimately, after what seemed like an eternity of cat-and-mouse, I came up behind the car, and sure enough, it was a last-gen ('03 - '06) Touran TDI (it's been facelifted for 2007). Seeing one was surprising enough. Even more surprising was the fact that it appeared to be privately owned. With apologies for the lousy cameraphone shot, you'll notice the oval decal on the left side of the rear glass (it was one of those things that symbolized Nantucket or Block Island or wherever). The tag, which is obscured by glare, was from New Hampshire. Apparently, living free includes scoring forbidden-fruit automotive machinery from the other side of the Atlantic.
However the owner came to posses the vehicle, a tip of the cap is deserved. It's a nice little van, and figure on it getting at least 40 mpg highway with the 2.0L TDI. It looked nicely-appointed, too with a large sunroof that was open, bathing the driver in light. Morst importantly (to me, at least), finding it and checking it out broke up the monotony of yet another brutal morning commute.
For better shots of what the last-gen Touran looks like, see below.