Hi Yemkik,
How are you doing? To your question, if you go through the CIC website, you will see it there as one of the requirements but I also think it is also at the discretion of the Visa Officer handling the case to either waive it or insist on the applicant present the result.
A friend of mine was ask to do it but the letter came very late and so he wrote the Visa officer and also included a letter from his University stating that his program was done in English and when the Visa officer requested for other documents, nothing was mentioned again about IELTS , guess the VO was satisfied with the documents.
In my case, I decided to do the IELTS even before it was requested from me, I also filled all the new forms when I heard that CIC was handling 2001 cases and so the next letter I got from CIC after the AOR was medical, police cert and proof of fund.
Hope this helps someone.