Well, since no one else has answered, I'll jump in with a guess...
What you saw might have been something to do with the Kynologischer Verein Rheinfeld-Möhlin - but the club isn't limited to BCs:
http://www.kvrm.ch/index.html
They do have an Agility group, though - and where there is Agility one usually finds a BC or two.

Might be worth a look.
Or, could it have been something to do with the Nationale Hundeaustellung für alle Rasen this weekend? Not exactly in the area, but I think not too far away - perhaps a group doing a bit of practice work?
http://www.nha-aarau.ch/index.php?id=3
Bear in mind I'm only guessing, and could be wrong. I often am.