I don't know what, if anything, in the way of non-Trane, is available to retrofit the controls on a Trane. I would think something is out there. In this area all the retrofitted Tranes have Trane's Adaptiview. I agree about supporting existing controls. Yeah, the original stuff is old, and the new stuff is better (in most ways). And so what if the vendor(s) don't want to build it anymore? Get another vendor. Or get a vendor to remanufacture the failed parts. For many years you could say Trane supports their chillers for virtually forever. I guess you still can, it just costs a lot more. And, if you don't plan agressively enough, it can cost some significant downtime.