I do know that the east side of Moors Valley is all private up to the ridge 4WD and this continues on as private around to Whiteman's valley too. The ridge 4WD which borders the water catchment and the catchment it self is completely off limits to all members of the public.
The whole Battle Hill, Hydro, Bulls Run, Totara Park area is largely accessible - the only private area shown on the topo maps is right in the area above Bulls Run. We did it years ago, entering from Bulls Run, and knocking on doors until we found the relevant place.
My usual approach to this type of thing is a session on the GIS system at the appropriate local council - usually fairly straightforward to find out who owns the land and give them a call. Mixed responses, generally I've been given permission but I've also been given the short sharp shift by a couple of landowners, usually culminating in the phrase "f&*&^n mountainbikers". Suspect others may have gone before me sans permission on those areas.
I did Welly > Battle Hill > Bulls Run Rd > Wainui stream > Dopers/Pram track > Karapoti gorge > Welly a couple of years back.
Memories are vague, but the scenery was pretty cool in places, with some tough climbing thrown in. The view from the hill above Transmission Gully out towards the inlet/Porirua is nice, and you get some interesting perspectives on the rows of huge electricity pylons running through the area. Also, you pass a sign that says "Dicks Yard". Excellent stuff.