multicast vpn could be considered an addition to the layer3 mpls vpn in order to transport customer multicast traffic. the simplest way is the inband mldp mode where the customer (s,g) route is encoded as a fec element and a core tree is built for each. more complicated modes available which use a bgp mvpn afi where customer (s,g) routes, type of core tree and a context label assigned by the sending pe router which have meaning only after the core tree label because it's not local to the receiving pe router. it can use nearly any p2mp procedure for core tree building.