Could be, of course, but, to be honest, I don't see it. - Rannos and Gremag already appear in "The Village of Hommlet", but unless I'm missing some integral piece of information, connecting them to Blackmoor seems like a stretch. - Especially in ToEE, there are elements (no pun intended) that allow for a closer proximity to Blackmoor. The Elemental Cult could well be connected to Zugzul, the demon at the bottom of the dungeon could well be connected to Tekumel/The Afridhi. If there was a possibl Blackmoor connection, then I would look for it there. 
As to a possible reference to a playtest - is Frank still active on the web? Would be nice to ask him just this.
As to a possible reference to a playtest - is Frank still active on the web? Would be nice to ask him just this.