Is AIXI capable of recognizing itself? If an AIXI agent were controlling a robot body, would it realize that the body's actions correlate with its own intentions? Would it pass the mirror test?
That said, things like the mirror test are so wrapped up in the construction of our own brain that it really doesn't make sense to apply alien intelligences, as you'd you'd be unlikely to get a visible response for unrelated reasons. "That thing in the mirror is me, so what?" Actually that's a bit misleading - the AIXI will have no internal dialogue. It's not built that way. But give it any task, and it will learn to do that task. If that task is to recognize itself in mirrors, it will... but it will do so in a way that is markedly different from humans.