That paper from Kempf, Wood, Ramzan and Gentry proposes to use multi-key CGAs as a way to secure address proxying.

Examples of address proxying include proxy-SEND (previously proxy-arp for IPv4), or Mobile IPv6, where the home agent locally claims ownership of an adress, on behalf of its real owner, because the owner is away from the network.

Pure SEND does not work in those cases, since it relies on a private key, that is not known by the proxy.