Sorry to dissapoint you all, but there are no messages passed through the chat channel about admins’ reaps or being available. The only other messages (not currently displayed in chat) are: tasks-locked, updateRealTimeStats, mesh-updated, cubeAdd and cubeDel.
updateRealTimeStats shows only number of players currently online (and it not so real-time, because it refreshes once in a few mins) and the others are self explanatory.
So, unless, I’ll find another way to gather the data, there will be no admins’ reaps.
As for admins availability, all I can think of, is using !online on all known admins’ names, but it would be a little bit spammy. Same for other groups (even more spammy).