With the release of iOS 6 I'd like to revisit the original question here: Access to Apple's built in Icons?
For example, when you hit the 'action' button to share a photo, now instead of an action sheet with buttons titled 'Message', 'Mail', etc., now there is a collection view of the icons for mail, messaging, facebook, twitter, etc.
For a 'share' action in my app I'd like to be able to present the same - because it looks better and would provide a consistent user experience. Is the use of these icons still not allowed, even if they are referring to (and would take the user to) the apps they originally belong to?