According to ADR check procedure you either switch off two faulty ones and use the good one or if all are bad switch off all three below 250 and change to BUSS and land. The icing may clear and may not be expected later but there is no way of knowing what was the problem with the faulty ones and whether it has cleared. A situation awareness decision has to be taken to land at a suitable airport. When that can be done with the remaining ADR what is the purpose of applying a non standard procedure with unknown results? Especially after QZ8501. Only in a case where during application of memory items and while applying ADR check procedure before switching them off the ADRS recover it is possible to leave them on. If a good one was rejected by two bad ones in that case the control laws wouldn't have changed(because of single ADR fail) and with the recovery of the bad ones it should remain in normal law. Although I do not think the rejected one will come back.