Let's start with something that is not actually a trolleybus, but does have a form of electric traction. Yes, I mean the electric hybrid bus. Something like the Toyota Prius I guess. I didn't know until recently that this technology is now applied in buses too. Enthusiasts say it's the next big thing, but people said that about the Hindenburg.
Canada got its first hybrid bus three years ago, May 2005, in a town called Kelowna. In an article dedicated to this event, busonline.ca states that "this new technology (...) will set the standards for fuel efficient, environmentally-friendly bus fleets in Canada".
BTW, for those who are interested, the article also explains how the hybrid electric system works.  Main advantages of course are reduced fuel consumption, reduced emissions and lower costs. The extra costs for the hybrid system can be recuperated in 10-12 years, with the average lifespan of a transit bus being 20 years.
However, the Kelowna hybrid buses were obviously not that big a success. In 2007, the Regional Transit System decided to forego hybrids in favor of new, low emission diesel buses. The savings realized from the hybrid could not offset its comparatively expensive purchase price (roughly $800,000, while diesels cost $500,000).
Of course this does not mean hybrid technology is dead. Other cities may have had better results. As they say, your mileage may vary. The best results can be achieved on a route with many stops, when a lot of braking and accellerating is involved. It's how the hybrid system works.
Toronto is still embracing the hybrid technology. If you want to see what the buses look like, I found this gallery with a lot of photo's.