Aussie, Aussie, Aussie... ergh
As an Australian I'm well aware of these issues but I think if you can afford to participate in the alpha, you can certainly afford to up your bandwidth cap for a month or 2. If you cant on your ISP, shop around, there's plenty of choice. I dont pay that handsomely for 500gb a month on 100mbit cable so the situation isn't that dire all across the country, but i understand there's places its not so flash especially out of suburban areas.
Because a lot of the universe is being procedurally generated i don't think we'll see have the WoW kinds of sizes of clients, but I'm gonna guess it'll still be in the handful of gig area by beta, alpha is anyones guess as they've said it'll be small portions of the game at a time but it could add up with several smaller downloads