I checked and did not see a way you could grab the region code from the command line. However, in the past I have modified the /etc/authorization file to allow users to set their own regions. There is an app you can drop into Casper to make this possible.
There is a setregion command in the DVD private framework folder, however Apple's manual page says you cannot use this from the command line. A quick google search shows people using perl to gather data and then run it through the binary. However, I never saw any results.