Apple would never make iTunes for Android though, so it's an unfair comparison. I have every reason to believe that Google would be willing to have its Maps application be the default.
I don't think any actual users realized that Google did not write the code for the previous Maps application, it makes no difference who writes the code. It was Google Maps, that's all that mattered. Apple already has exclusive rights to approve all iOS applications, so having a third party write the code would not be any more of a risk than shipping an internal app everyone knows is powered by Google.