That's actually a good question. From a pressure standpoint it might be fine, considering subsonic .223 isn't that much more powerful than a .22 LR. But the Pilot 2 has aluminum baffles and -- if I recall correctly -- isn't rated for anything more powerful than .22 LR, so it might be pushing it. I'd also be worried about bullet stability with the long, subsonic .223 ammo, but that's an issue no matter what kind of silencer you're using. Ask AAC, they can tell you if it's safe and -- more importantly -- if it's covered under warranty if you shoot subsonic. 223 through it and something goes wrong.
But I have to ask, "why"? It won't cycle the action on a semi-auto and it's barely more powerful than a .22 LR. Almost nobody uses subsonic .223; everyone I know who uses a silencer on a .223 rifle uses supersonic ammo, including myself. Just shoot .22; it will have pretty much the same ballistics, but it will actually cycle the action and will be a LOT cheaper.
In over three years working at gun shops I've never had anyone ask for subsonic .223 ammo who was actually serious about it and knew its downsides.