Douglas reports: One is for IP routers to route e.164 addresses in the same way as they do IP packets. In this scheme, gateway advertisements would occur via a modified IP routing protocol (BGP I think it was).

yes, this idea was mentioned but the person who presented it called it "a bad idea" most people who run Internet service providers or who deal with routing protocols fully agree with that conclusion

as Douglas noted the state of much of the effort is a "still-debated problem definition"

Scott (Area co-director for Transport in the IETF, the area in which this work is being debated)