PR move wise, they've already won the PR battle. Everybody who owns an iPhone 5 or everyone who has considered buying an iPhone 5 now knows that Google (and now Android) has a superior maps offering. By offering a Google Maps app on the iPhone, it just gives customers one reason less to stick with Android.
It will be hard for Google to prove the anti-competitiveness of the App store. It would be quite interesting though - Android has the ability to use different App stores, while Apple certainly does not. It sounds unfair, but I wonder if a court feels the same way.
Pretty sure Apple will be at a disadvantage for years regardless. They've never been a data company as it is, and there's no reason to believe that they could suddenly go out and put together their own maps like Google has done. Better maps does not necessarily equate to having more usage data either.