If they don't allow a Google Maps app on the iPhone App Store, or if they drag their heels in approving the app, especially given all the outrage from the customers, I believe this is clearly anti-competitive behavior.
Once Google has one available, if Apple doesn't readily approve it, I think a very, very strong case could be made that they are holding back Google's app in order to help their App gain traction. Since only Apple has the power to approve or reject apps from the App Store, if that isn't the definition of anti-competitive, I don't know what is.