And the criteria for determining what is and is not art?
The key criterion is creativity and expressive/emotional content, and wherever that comes from, that's the source of the art.
In this case, some of the robot's paintings are quite artistic... but it's not the robot that selected the subject, captured the right feeling, chose a composition that accented it, etc. What happened here is that the robot reproduced some artistic images that were created by a human. Art? Sure. Robot art? Nope.
In the case of your hypothetical art Turing test, where only the end product is available, sure it's quite likely that we couldn't distinguish between the computer renderings and human work, and we'd call the computer renderings art... but the creator would be whoever provided the computer with the input -- code and/or data. Human-created art in the medium of computer-controlled paintbrush, for example.