Personally I didn't even know what trolleybuses were until I saw your post. Googled it just right now and I have to say that it seems like a novel idea. I cannot say how effective they are in big city but nevertheless a lot of people will just get the bus for the novelty of the ride. I know because given a chance I surely will :-)
Perhaps they are trying out just one trolley bus and if the idea succeeds they'll introduce more. I'll probably be checking out on how these buses are doing as the time passes.
It actually might look like a novel idea with more attention being towards electrification of the means of transportation but trolleybuses were very common in the past. Good to see them back!
Yes, I looked further up about it on the internet and found quite a history of their use. The earliest prototypes date back to more than a century. It is a bit of an adventure itself, learning about them :-)