Yeah. I'd be surprised if Apple didn't use similar logic. XMPP can do multiple ports (a deployment can specify the recommended order in DNS). I've not heard of an all-ports deployment, but it does sound like an interesting experiment :)
Apple has a bit of an easier time, because they can (and do) lean on cellular carriers that restrict access to their push servers. And they have 17.0.0.0/8
But they say port 5223 and 2197 with fallback to 443 [1]. Google says 5228-5230 and 443, with a couple outliers [2].
