any possibilities ? and what are the chances that this defector could be a mole (double-agent) planted by the PRC
The Aussies are considering this possibilty, Im sure
I don't think that's the problem. Even if he were (and of course there is a reasonable chance that he is), you still don't handle the situation this way. If he is a plant, then that still doesn't make him useless by any means, just he needs to be handled with a bit more care.
Even if Chen is just a kook (and I personally don't think so at this point), our behavior is not helping our case with any future defectors seeking asylum. You can be sure that the political classes are watching this situation in China, and when they see how this guy is being treated, it is not going to encourage further defections.
Zero possibility -