That's a good question.
Well, I read several forum discussions and it seemed to me that people get phone interview only when they live somewhere in remote area (remote in relation to the nearest CIC office).
Also, several people wrote that they got a letter (not an email) with date/time of the appointment. So, I was under the impression that a letter notification is a regular way for the appointment notification. However, theoretically they can call to book an appointment.
It would be nice to hear from people who already had their interview scheduled - was it letter/email/call and was it phone or in-person interview?
When i got mine it was just an email from my local office letting me know the date and time of the interview and what to bring.... That was the first i heard about getting approved haha. 3 days later i got the AIP and DM which was funny haha