Not sure why this matters..
BlackBerry's are actually far more common than iphones in other markets. I don't think this is realy aimed at US markets. In Panama and other latin american countries everybody has a blackberry because of this ability to chat for free because of the high costs of SMS's and iPhones are really expensive for most people.
What I don't understand is what BB hopes to gain from this. It is a free service that allows people to chat with other BB users without buying a blackberry. This will only hurt their sales.
Apple was stupid not to allow integration with BB messenger a long time ago.