There is still a rule in the guidelines that mentions "Apps that duplicate Apps already in the App Store" though it doesn't specify whether those apps are Apple

There is still a rule in the guidelines that mentions "Apps that duplicate Apps already in the App Store" though it doesn't specify whether those apps are Apple's own, or any other developer (in fact, comically, the rule lists "fart apps" as an example). They don't really say how many apps of a certain type will be accepted into the app store before this rule goes into affect. They also have rules against "Apps that look similar to Apps bundled on the iPhone", "user interfaces that mimic any iPod interface" and "Apps which appear confusingly similar to an existing Apple product" I think basically the guidelines are written to allow Apple to reject apps with it's own discretion when it doesn't want them in the store. Whether that be for business reasons or otherwise. In the case of map apps, they seem to be rather lenient. I wonder if that's more of a grandfather type situation because they didn't have their own map app before iOS6.