A few days ago, Waitemata Local Board member Christopher Dempsey confirmed that using the old Parnell Rail Tunnel for cycling is indeed feasible.
This makes a Greenway from Newmarket to lower Parnell (and onwards to the Grafton Gully and Beach Road cycleways!) much more realistic in the short term. As Christopher notes:
An engineers report commissed by the Board has recently confirmed the suitability of the tunnel for a pedestrian path and cycleway, subject to several constraints that need to be managed.The engineers report the old tunnel is in really good condition.
Awesome. Hands up for who wants this Greenway yesterday? One of the upcoming topics for the election will be greater Greenways funding!