I already have a DSC radio on my easySPLIT. Vioce, AIS and FM radio are all O.K. However I am not sure if the DSC radio transmittes if the relay switches too slowly.
A normal radio needs ca. 20ms to build up transmission power. Only if the radio has built up its transmission power, the DSC signal can be send. (Of course, if else the signal would be transmitted without power). Meanwhile you can send a DSC Message without problems.