the long-standing practice that unknown primary returns under CTAs and airways are deemed to be vertically separated from traffic inside CAS,
Windfarms cause clutter on primary radar.
To get rid of the clutter, the primary radar will be blanked over the windfarm.
So, there is nothing to deem OCAS.
However, there needs to be some assurance against possible airspace infringers
Hence a TMZ.
The TMZ is temporary because when the new centre comes on line, the radar at the Kincardine Bridge will fill in the gap that is currently blanked.
If you read the letter that was posted by FBW properly you will see that this was not a consultation. It's not an airspace change so it's not covered by CAP724/725.
The CAA put this measure in under their exisiting powers to preserve airspace safety. They've always ben able to do this - even before the TMZ policy.