Zürich Tram Drawings ~ Tuesday, January 20, 2009
The VBZ also has a page of scale drawings of their trams (and busses).
The files are in PDF format and look like they would resize nicely (i.e., they are actual line drawings rather than scans/bitmaps), so it would be possible to print out copies scaled perfectly for building a model in whatever scale you like.
I wish more transit operators were so considerate of the needs of modelers.
Many thanks to Andrew Moglestue, author of the Trams of Zürich website, for directing me to this.