Do you really need to break iOS encryption? I'm not a big pro in iOS but I heard there are many forensic companies which specialize on extracting data from iOS devices, and from their pages[1] it looks like you can extract quite a lot of stuff from somebody else's phone.
Wait, so there's a backdoor, but police doesn't own it? Then I'm pretty sure NSA either has it or has a way to make Apple tell them how to use it, and it is done is some "security letter" manner that doesn't need a warrant and permissions from any non-kangaroo court. This is how these things are done these days. In any case, this confirms the backdoor exists and Apple has official queue for police to use it. One can only guess who else can access it and with which procedure...
Their 'physical analyzer' doesn't work from the iPhone4S or iPad 2 onwards (under Click here to view all supported iOS devices).