The iPad's operating system, iOS, makes the orientation of the iPhone and iPad available to a developer to use in their app if they choose to do so. It's entirely up to the Developer as to whether they use this information because it might well be that re-orienting the app display is inappropriate to the content. As a result, when an iPhone app is imported to the iPad it will inherit the original app Developer's intention and, if they chose not to make the app orientation-aware, then it is impossible to over-ride that. Those iPhone apps, however, that are orientation-aware will automatically align themselves to either portrait or landscape mode if the orientation lock is disabled.
Tim
