My understanding of RFC 4363(10a) is that it is intended to be used to provide reach from one MPLS network into another MPLS network in another AS for the purpose of providing carrier transparent support for MPLS VPN customers that have a physical presence in both networks.
However, could RFC 4363(10a) be used between two carrier networks where one is an MPLS network and the other is a native IP only network? The desire being for the native IP network to be able to provide IP services such as VoIP to customers built on the MPLS network. If so, can someone point me to documentation and example configurations for this type of setup on the non-MPLS side? I have been looking at section 4 of "Implementing Advanced Features on MPLS-Based VPNs", which if I'm reading correctly applies in this type of situation.