I think you have to buy a BE 2010 RAWS license and then speak to our custoemr care about a downgradeed serial number for BE 12.0 - as we stop selling licenses for older versions as newere versions are rleased and 12.0 is 2 versions old.
As I am not 100% sure about this if you ring our support lines and ask to speak to someone about sales/licensing you should be able to get some advice. Failing that speak to your resellers and get them find out how to get a license for an agent for an older version.
Umm I am not part of licensing - and this is a general community supported forum that is contributed to by users of Backup Exec and Symantec staff (when they get time) you will need to speak to someone (either at a reseller or in our customer care/sales teams) to take this further.