3GPP 23.040 section 18.104.22.168.13 defines additional information such as NUMBER_OF_VOICE_MESSAGES, VM_MAILBOX_ACCESS_ADDRESS. Besides, "In the event of a contradiction between ... then the Enhanced Voice Mail Notification specified here shall take precedence."
This feature is still not implemented in present Android ICS release and is therefore marked as enhancement.
Unblock b2g-sms temporarily for milestone 3.
Please this into backlog.