battle.net is included in any Blizzard product by default. There is no download that occurs. What you need to do to get the latest version is to fire up Warcraft 3 (or whatever Blizzard product you're using, World Of Warcraft doesn't use battle.net btw)
And then it will check the version (and download the correct copy) itself.
If you were referring to if there is a standalone upgrade for battle.net somewhere that doesn't go through this mechanism (and you'd like a local copy / download of it to save on bandwidth) then i'm afraid I won't be able to help you.
Google "download battle.net 1.2.2" or something, and then request someone with uncapped bandwidth upload it for you to a local server.