Finally here is something more concrete on this project, with video and quite a bit of detail on what's happening:

http://tramways.weebly.com/electric-bus.html http://tramways.weebly.com/electric-bus.html

The work is being done in NZ Bus' Wellington workshop. Somebody should try to sneak a look in there. The reference to "October" is October 2016 so it's substantaiily delayed, which is the reason for the trolley system's life extension.
Tony P
(who notes that a diff is apparently called a duff in New Zealand ;))