Yes, All Real NZ and Godzone scenery released since Real NZ Nelson, and including the Subscription, works with FTX NZSI. There is some extra information here.
There is also a great set of screenshots from Mallard on the FTX forum, although you may need to be a member over there to view it:
Southern Comfort, a flight from FTX NZQN to Real NZ Dunedin. Note that this starts at Orbx's Queenstown, and ends at Real NZ Dunedin.
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