Only references I've seen to the Enclave is their Fallout 2 power armor, a rare mention from the Brotherhood of Steel, and a pre-war Boston Bugle article about the President and his staff fleeing to the Poseidon Oil Rig "Control Station Enclave" off the coast of California.
Personally, I'm glad they're not in the game. Their presence in Fallout 3 was already beating a dead horse, and New Vegas gave them such a great send off... bringing them back again would only cheapen that.