It seems that RCON/Battleye messages aren't hooked into the event system on the server side. They probably go from the outside (cftools for example) into the RCON server, and are then either executed (player kicked, banned etc) or broadcast directly to the clients.
It would be great to have something like RconMessageEventTypeID in OnEvent(), or enable the BattlEye channel with ChatMessageEventTypeID, whatever is better architecturally. Probably RconMessageEventTypeID, since the RCON chat messages are just a subset of all RCON messages.
On the client, the BattlEye channel is part of ChatMessageEventTypeID, but not on the server.