At the 'Main' menu select the 'Community & Extras' option and highlight the 'VIP' selection. Then press the Triangle button and input one of the following codes (without the quotes) to unlock the corresponding unit.
Unlock Russian Spetsnaz Guard Brigade Enter the code 'SPZA39'.
Unlock Special Spetsnaz Battalion Enter the code 'SPZT17'.
Unlock European Enforcer Corps Enter the code 'EUCA20'.
Unlock U.S. Joint Strike Force Enter the code 'JSFA35'.