You can -technically- do anything in Haxe that the underlying platform is capable of, by either using code-injection with untyped magic and meta, or by adding your own files with FFI.
When it comes to the camera, though, while you can take a picture relatively seamlessly, if you want a streaming display, you're going to need a native surface, since that's the only way the iOS is capable of rendering the camera stream in real time. Game engines like HaxeFlixel usually cover their screen with their own control, so getting your camera feed in there can be problematic.
But, like I said, if all you want is a picture, you can capture it without needing a native surface in the UI tree. There are appropriate methods for doing it.