My understanding from Cogent (our upstream provider) is we provide them with a letter from ARDC allowing us to advertise the sub net to the other AS machines around the world.  They put the sub net in their AS then magic of the Internet it routs to our server/users.  I am not a Computer Science major or person so I am just learing how things work up stream from the ISPs.  So correct me if I am wrong.
 
Tim the reason for not doing IP tunnels is easy.  Single point of failure.  God forbid SCSD drops in to the ocean (not really but lets just say the big one hits SoCal) all of AMPR is down.
 
Lin