Not sure where the overlap zones are but Derby is mainly big old trees
I have not read into it too much as here in SA, a load of trails are/were built in working forests.
We still have Prospect Hill, Gate 19, Kersbrook and Kaiserstuhl to name a few that spring to mind.
Can only think that the reason they were built there was that Forestry were just 'growing trees' to cut down and didnt mind MTBers riding there. NP's, Reserves, Conservation areas etc, do not want bikes through their land/area - though we do have access to a quite a few in SA thanks to the hard work of many.
Its been all part of the deal... ride yer bikes here but we are coming for those trees at some stage in the future, there will be a thinning session that will make a mess of the trails, but can be rebuilt. Then the big cull usually trashes the whole joint up.
Tassie might meet with some resistance for building bike trails in future logging zones... unless well compensated for lost revenue.