Ok, I'm thinking, like most games, MW2 will use specific ports and protocols to communicate. I acknowledge that the Steam traffic will still need to be accounted for since, but I don't see what is stopping WA from simply allowing traffic that falls into a certain range in terms of protocols/ports to be free, particularly if nothing else uses that range.
It's easier to manage with a dedicated server, but I think it's possible (probably just difficult) to do for MW2.
But what has me wondering, apart from the bandwidth being free, how is WA going to draw players to their servers? Ultimately people play where the majority are, and if the WA servers are quiet then it's ultimately pointless.
Also, my trial account was super fast. Excellent p2p and much faster speeds on youtube/fb and various other art forums I visit.