The IS Content Server is open access according to the steam powered website.
They are an official mirror on the
www.steampowered.com list. Some servers are specified to be a closed user group but that does not include Internet Solutions.
I have noticed it still uses my international connected between like 15kb and worst 40kb a second, but then like 150kb - 400kkb via local only account.
If you disconnect ur international connection while downloading it carries on with local only however as of late for some reason it stops after about a minute or so and gets going again, but sometimes it doesnt. Maybe it needs the international to recheck sources or something.
I just know the majority goes through the local connection.