I have been doing some testing and have found that with 30 bombers (flying) on the isles of doom map that the server is using 160-70 kbps when i am connected.
When i join the channel map with no AI the server is using 30-50kbps for my connection but as soon as i spawned an extra G50 it shot up to 110kbps and after 5 AI spawned the server was using 190kbps for my connection
that channel map is a massive resource hog