Around 5 years ago I had a male convict and female mbuna breed together. The convict was extremely PO'ed at the mbuna for just "eating" the eggs, but regardless of her holding the eggs they never became fertile and she eventually did eat them. But yeah she did hold the eggs for a few days before just giving up and eating them.
I've seen other Africans cichlid try to cross breed with SA cichlids but never once seen any viable fry as a result. Personally I'd agree with most everyone else saying that they are just too genetically different to get the job done anymore. It could've been possible in the past but we will never know.