I love this idea. i will look for it in Sydney. When I was living in Germany there were similar systems in the supermarkets to recycle some kinds of plastic bottles. They even gave you back a few cents per bottle and people were often leaving bags of bottles to homeless people to allow them get the money.
There is an exstensive research on how BPA ends up in our bodies when we eat fish because fish eat plastic and it is very scary to think about it. This is a good idea, but I believe that it will have just a small impact on the problem because of the size of it. However, the good point is that together with the effort to reduce the use of plastic it is important to eliminate the plastic that is already on our oceans and landfills and treated as waste.
However, I have a question: how can you be sure that this mechanism does not damage marine life?