It's not so simple in 12.04, especially if You have clean server installation (without GUI). The new NIC is showing up as new only if You have had identical installed in Your system. In this case new NIC creates new line in udev.rules. But change content in udev.rules does change nothing (when You want to change interface name). Older ubuntu versions supported that.
If You replace NIC to model, that was not used in system before - system is not detecting it, even not creating new record in udev