Hello adjacency is brought up using link Hello packet with source IP address set to the interface borrowed IP address and a destination IP address set to 224.0.0.2.
As a consequence of (1), Hello packets with the same source IP address should be accepted when received over parallel unnumbered interfaces from the same peer LSR-ID. The corresponding Hello adjacencies would be associated with a single LDP session.
The transport address for the TCP connection, which is encoded in the Hello packet, is always set to the LSR-ID of the node regardless if the user enabled the interface option under config>router>ldp>if-params>if>ipv4>transport-address.
The user can configure the local-lsr-id option on the interface and change the value of the LSR-ID to either the local interface or to some other interface name, loopback or not, numbered or not. If the local interface is selected or the provided interface name corresponds to an unnumbered IP interface, the unnumbered interface borrowed IP address is used as the LSR-ID. In all cases, the transport address for the LDP session is updated to the new LSR-ID value but the link Hello packets continue to use the interface borrowed IP address as the source IP address.
The LSR with the highest transport address, that is, LSR-ID in this case, bootstraps the TCP connection and LDP session.
Source and destination IP addresses of LDP packets are the transport addresses, that is, LDP LSR-IDs of systems A and B in this case.