I always had the asumption, that MJ worked on parts of the Cascio tracks, some may just be some melodies (with a working title maybe), maybe some were more fleshed out. Other were maybe just shown to Michael. At the end, no song was finished or close enought to finished to be released, but Cascio wanted to sell them so he faked them. Maybe he even just those demo, with maybe same scratch vocals or just MJ talking about ideas (like he did on Hollywood tonight) to convince the estate, that the songs are real.