I don't believe that AS701 does it. I seem to recall this from
hearing about some very complicated process that had to be completed for route-views.oregon-ix.net to get their AS701 feed.
This may no longer be the case but seeings as the feed isn't there anymore, i'm guessing they still don't do this.
I know for a fact that it can be done. I have had this set up with AS701 when we were a customer (>4 years ago). Everything about our set up with them was very specific and broke a lot of their rules because of the kind of usage we were putting on them -- they made a lot of exceptions for us. I am sure none of the guys that were helpful then are still there now, and moreover, I am not sure if it was because of our size that they were able to make the exception. I am just chiming in because I know that the exception has been made on more than one occassion for us. In fact, we have had BGP views (EBGP-multihop) from several core routers backhauled to us at different times, and for different reasons. This is all ancient history though. Deepak Jain AiNET