So I'm from Malta, and we don't have the PS Store yet here (believe or not).
My main account is Maltese, PSN works fine, I can add friends and play online games.
But I have a secondary account which is Italian, I use this just to purchase DLC and games.
The games and DLC are compatible throughout the whole PS3 ecosystem, so I can login with my Maltese account after the purchase, and play RB DLC both on blitz and RB3.
I havn't had any trouble playing online with my maltese account on RB3 with DLC i download from my secondary account.
I play DLC on blitz no problem and have successfully linked my maltese account with my FB account.
I have successfully initiated a scorewar from the game with a random dude and worked flawless.
I noticed that FB knows what DLC the user owns before you initiate the scorewar i.e. you cannot initiate a score war with a FB friend if the friend does not own that specific song.

Hence my query:
Can people challenge me in a score war on FB if the (maltese) account i use never purchased any DLC?

sorry for the long post :/ just trying to be clear