I am in the same situation.. I guess CIC do landing interview for inland CEC applicants... I have been searching the forum, it seems like interview is just a part of process, doesnt mean anything negative.
Mine was approved on Feb 20, no news ever since. My understanding is that scheduling interview could take longer than getting PPR...
My visa office is Vancouver and I read it could take upto 3 Months to schedyle interview at Vancouver office.. which is frustrating!!
But good part is that you get PR on site after interview.. no need for flagpole