I noticed that too. Going through the contacts it wants to use the Apple Map. Anyone know it this can be changed. I know there is a suggestions place in the Google Map somewhere. I can't see Apple letting Google reach into the Apple Contact app though.
Actually Google could, if they wanted to, reference the contact list under iOS. In fact iOS 6 has a privacy setting just for limiting access to your contacts.
The issue is direction. From Google maps you can access your contacts. From contacts you can only access Apple Maps. And the odds of that ever being changed is almost zero to none.