I think you're right. Mind you I don't know of any successful straight electric double decker in commercial service anywhere yet.

https://www.metlink.org.nz/news/electric-buses-confirmed-for-wellington-fleet/ https://www.metlink.org.nz/news/electric-buses-confirmed-for-wellington-fleet/

But: http://www.gw.govt.nz/brand-new-buses-headed-for-wellington/ http://www.gw.govt.nz/brand-new-buses-headed-for-wellington/
"How does this decision relate to the future of Trolley buses in Wellington?
The decommissioning of the trolley buses is a separate process that will be completed in October this year.
Development and testing continues by NZ Bus on the development of a plug-in range extended electric bus that will re-use and refurbish the trolley bus fleet.
GWRC and NZ Bus have detailed transition plans in place to ensure that bus services continue to run during the transition from trolley buses to the new converted fleet, which may require the use of diesel buses until the conversion programme is complete."

Tony P
---InTramsDownUnder@..., <matthew@...> wrote : But it appears the bus company backing the conversion lost most of their
Wellington route contracts to some one else.

The project probably halted the moment it became apparent that NZBus
lost most of Wellington to Tranzit.

After putting their own money into the conversion they are hardly going
to hand the vehicle over to a competitor.