I found this today. I explains a lot including that there are two different proposals being looked at. It seems if anything is going to happen with a desal plant it’s not going to be soon.
thehill.com

Project would pipe water from Mexico to parched Arizona — if anyone can agree on it
As arid Arizona scrambles to quench the thirst of a rapidly expanding population, officials are eying the Sonoran seaside in Mexico as a potential wellspring for future demand. But whether th…
