According to a recent statement from THQ, UFC Undisputed 2010 will be including a code that activates the online portion of the game. Those who buy the game used will have to pay $5 to activate the multiplayer content of the game.
So it seems like THQ is also catching on to the new release code scheme, but in a pretty bad way. Blocking off something as big as the entire multiplayer mode is a pretty dirty scheme to get players to purchase new games as opposed to used ones. At least it's not an entire $10, but $5 is still a pretty hefty price to pay when it comes to a part of the game as crucial as the multiplayer.
Either way, players can look for UFC Undisputed to release next week on May 25. Whether the multiplayer used aspect will work out or not is yet to be seen.