BNN is reporting that AT&T considered entering the Canadian market (similar to Verizon) but believes the market is too small to support a 4th national carrier.
Interestingly AT&T had a sizable ownership stake in Rogers in the early 2000's (selling their shares back to Rogers in 2004). Shifting Canadian foreign ownership rules are allowing these foreign entities to re-enter the Canadian market but they are all finding the market too small.
The real marker of interest will be who actually bids on the new 700mhz wireless spectrum auction. Could one of the smaller competitors bet big and try to become the next national player?