[stvkr-a-fotos] Wiesel bus question

When I was in Wien in April I photographed a couple of Wiesel Setra S419UL buses.

A web search turned up Wiesel buses in St. Pölten but the buses I saw had W registrations such as W6304MW which I thought meant they were Wien based buses.

I noticed that Wiener Linien buses had registrations ending LO and Dr. Richards had them ending in MW.

Are Wiesel buses and Dr. Richard buses part of the same company because the registration ending MW or is that a co-incidence?

Is Wiesel bus a tariff association?

Regards
Michael Taylor
Binbrook, Ontario
http://www.michaeltaylor.ca