<<According to what I could find out, it's about as German as Häagen-Dazs... and I'm not even sure if the dots above the U were originally supposed to be part of the letter... ZUM would make more sense considering the explanation on http://en.wikipedia.org/wiki/Z%C3%BCm (assuming spelling based on something like the International Phonetic Alphabet).
If it actually IS German, I'm pretty sure it's an acronym, but I'd bet on a somewhat phonetic spelling of "zoom".>>
The dots are there, this is the start of Brampton Transit website for the service..
http://www.brampton.ca/en/residents/transit/zum/Pages/welcome.aspx
Regards
Michael Taylor
Binbrook, Ontario
http://www.michaeltaylor.ca