No, Alastor DMc, I think that Nintendo wouldn't go to all these great lengths just to fuse to get a move that you already could get. I think that they would have called it a move combination power up, or something like that. XD
And, yeah, if you could trade the Rescue Force Pokemon to D/P, then why not bring along their fusion moves? Also, they wouldn't make dual moves in D/P just to put them in Dungeon, and make them just be a better move, like Surf. XD
And CB, they'd certainly have limits. Like only same class moves, plus limits on that.