I have WiSM A and B setup in a mobility group. According to the GUI everything is available and works quite nicely. On both WoSMs I have the same identical WLANs (SSIDs) setup with WiSM interfaces in the same VLAN.
Now, what happens when WiSM A revoots is that all APs instantaneously fall over to WiSM B. This is what I want. All the clients are also visible on WiSM B. However, WiSM B does not learn the IP adresses of the clients (do not know if this is needed for redundancy or only for REAP) and no client can communicate.