Never heard of treatment of psychosis with ayahuasca or MAOI's.
Nevertheless, some types of depression or psychosis are very alike and realy more like something in between a severe depression and psychosis. In these borderline cases, where the diagnose realy depends as much on the preference of the psychiatrist for one diagnose or the other, as on the condition of the patient, i can imagine that sometimes treatments that are known to be effective for depressions can work out very well.