This is standard practice for any NCIB. It doesn't mean that they repurchased all of those shares. Looking at their 2011 Annual Financial Statements, it reads:

During 2011, we purchased 4.8 million Class B shares at a cost of $171 million pursuant to a normal course issuer bid. Of the shares purchased, 4.3 million were cancelled prior to December 31, 2011 and the remaining 0.5 million were cancelled in early 2012. The normal course issuer bid, which commenced on June 27, 2011, allows for a purchase of up to 40 million Class B shares and will continue until June 26, 2012 or an earlier date if we complete such purchases.