Sorry, I tried to delete this thread as I just found the answer myself, but it wouldn't let me.
In case anyone else is wondering, we're running 6.0 and this is the
WikiEvents_Page(Telligent.Evolution.Wikis.Components.Page page, System.EventArgs e)
event. page exposes a wiki object, and a sub-object is group.
I do hope someday that wiki's will join the rest of the applications in their one united set of access objects instead of us having to double all our current code just to support wikis.