The WBO has stripped Joel Casamayor off his interim lightweight belt for not fighting Campbell, therefore, his match against JMM will NOT be for the WBO interim lightweight title, but only for the Ring's title!
I had the WBO on the phone, they stripped him actually a while ago, he had five days to sign the contracts with Campbell, but didn't do so. If it would have been the other way round, they would have stripped Campbell, and Casa would have immediately become full champion.