As you stated Getty won't want to deal with you on this, they will want to deal with your clients. In essence your clients would have to hire Oscar, and them you would / could reimburse them. The letter he drafts will get getty off your clients back, and they still won't accept a low-ball offer, but it puts the ball firmly on their side. The whole point of this forum and Oscars' letter is to not pay what they demand, but rather perhaps pay a reasonable amount. Getty however is not reasonable. Chances are good if your clients hire Oscar, it will go away..albeit after the 3 years SOL. In my case which is a bit different, I had Oscar draft the letter and never heard anything back for a long time, until they did come back with a "reduced settlement amount" which I quickly declined. I am now nearing the end of the road and feel fairly confident i will not here from them again.
I have also had clients receive the letter for images they supplied to me as their web developer. Even tho I was not responsible I suggested they hire Oscar and I credited them back, so in the long run it did not cost them anything except a little time and aggravation.