Currently emerge --search --usepkg can display local binary packages, but we could add --getbinpkg support for it to include remote binhost packages in search results. It might just work if we simply populate the bintree with getbinpkgs=True. We could also add a --bingpkg-respect-use filter or something.
It already works with --getbinpkg because run_action calls populate for the search action. I'll think about the --bingpkg-respect-use filter idea some more.