Does anyone know if the International Assist feature on the iPhone works when dialing a number using the tel:// URL scheme from an application? For those unfamiliar, IA automatically prefixes the "+1" to US numbers when using the iPhone internationally. I know that this works when dialing from either the built-in Contacts or Phone apps, but can't find anything stating that it works when dialing numbers from an application. Also, is there any documentation as to whether this feature is included on Canadian (Rogers) or European iPhones (or is it only used by AT&T)?

If IA does not work when dialing with a custom app, can someone point to the API that would allow me to detect that the use is roaming on a foreign network so I can essentially duplicate IA's functionality?

Any help greatly appreciated!