PPL cannot license recordings that are licensed via MCPS, such as production music and library music as there would be a duplication of rights (PPL and MCPS both license for the public performance and broadcast of the sound recordings).
PPL’s role is to license sound recordings that are created for the purpose of being sold (or made available) to the public. However, if the public performance and broadcast rights in the sound recording have not been licensed to any other party then PPL should still be able to license them.