I doubt there will be much in camera's on rural roads. Rural roads = less traffic, thus more cost than revenue to make. (That is if they're back roads, and not highways). And since camera's are all about revenue... I strongly doubt there will be a camera blitz.
Edit: Then again this is the labour government, and they do like running in the red - so I could be wrong.
I'm going to go out on a limb and have a different theory. No - this isn't for revenue raising this time....
But it's also not for safety....
.... it's for redirecting money from maintaining our rural roads to other areas.
There are already a number of rural roads that have been left unmaintained and degrading. The government doesn't see it can buy votes in certain rural areas - so wants to redirect it's cash away from maintaining roads in those rural areas to other locations.
They have been dropping speed limits on sections of these roads. I think this was a trial, and now they want to go wide spread with it all. It's about redirecting finance elsewhere, and leaving certain country seats to degrade.
I'm sure others who travel in rural areas have seen speed restrictions in the middle of no where simply because the road surface has degraded and the government won't fix them.
Whether we obey the speed limit or not it won't matter - the roads are going to degrade more... and with the worse surface you won't want to drive on them at 100kph.
This is just the opportunity the government is using to excuse themselves from not maintaining our roads and to buy votes elsewhere so people can't complain about the road surface not being suitable for the speed zone.