Multicast packets cannot be forwarded or received from an LDP LSP. This is because there is no support for the configuration of such an LSP as a tunnel interfaces in PIM. Only an RSVP P2MP LSP is currently allowed.
If a multicast packet is received over the physical interface, the uRPF check does not resolve to the LDP shortcut because the LDP shortcut route in RTM is not made available to multicast application.