In http://arxiv.org/pdf/0901.3262v2.pdf I have described this in some detail and constructed an explicit counterexample to the hope that one can derive it somehow given only the Hamilton operator.
Some quotes from Zurek (arXiv:quant-ph/9805065, arXiv:0707.2832):
It would be indeed useful, but, unfortunately for MWI, it is not possible. At least not without any additional physical structure.
So have you talked to him about this?
Last time I saw an interview with Zurek he was fairy confident in MWI, though he also said that it might be that you can get "it from bit" some other way.