I'm pretty sure that they will have the same limits as people on the ground in that they can't fly over water, the black malas masses, and in fel they will still hit objects on the ground (ie trees, shrubbery, tombstone, etc), otherwise they would have way too many advantages over human and elves. I think the special areas the FOF was talking about is sorta like Wind is for chars with magery.
This is from the May 1 FOF.
Will flying be possible in the felucca or just in the new areas introduced with SA?
Er, yes, yes they can fly anywhere.
Flying lets the Gargoyles move at mounted speed, and also access special areas that would normally be impassable to the earthbound creatures.
Ter Mur will contain most of those special areas, but the other facets will have a few as well.
Regardless, Gargoyle can *fly* at any time, as far as movement speed goes.
-Draconi