Amtrak runs on the UP line there. So it most likely has to be a signer on any agreement potentially affecting its service - like a major new connection. Whether it will use the connection or not isn't really the point, though as some have mentioned if Amtrak ever DID need to do a detour on BNSF it would make life much easier than the previous scenic tour of Richmond. I really doubt that Amtrak (or BNSF) would want Amtrak running frequently on the canyon line - too much BNSF traffic, and besides Amtrak has a lot invested in the Martinez station that they wouldn't likely want to throw away.