Not personally, no. But I have known quite a few people who practiced at The Royal Children's Hospital in Melbourne who have come to the US for one reason or another. Additionally, I known a person who trained in Sick Children's and went to practice in Australia. And, I have heard of one person, who trained in the US going to Australia for 1 year as a junior attending/senior fellowship... a Registrar I think is what the position is called. So, needless to say, it certainly is possible.