My understanding was that YA gets shelved in...YA. And that's all anyone can do about it. If it's adult fantasy, then it gets shelved with fantasy. If it's YA fantasy, it's shelved with YA. If it's YA romance, or mystery, or urban magical suspense realism, it gets shelved in YA.
Maybe that trend has changed in bookstores in other parts of the country, but not mine. Anyone heard differently? The size and growth of YA certainly makes it look like breaking it down to subgenres in the bookstore isn't far off.
$0.02
ETA: If you're talking about how to phrase it in a query letter to agents who are looking for a certain type of read, I suppose that's a different thing; just know that when it gets to a publisher, and then to a bookstore, it's going to be shelved with YA.