interesting question, the viewing of the other players IP address is (by default and common sense) allowed only in peer2peer multiplayers which is sometimes used in DirectPlay games.
as far as I remember the vietcong's multiplayer is not p2p so no packets should be exchanged directly with other players and then it's udp based so there are no connections established to/from other clients.
obviously you can verify everything using a sniffer (for example
http://www.wireshark.org) during the connection to a server and you should see only the packets to/from the server