Bren, I can tell you I've experienced a "4 way" in the hold at BNN. The a/c entering the hold at the top started the whole thing while the 3 aircraft in the hold were all just about to turn inbound (sods law). Avoiding action was being dealt out left right and center but TCAS certainly got involved (from memory there were 2 RA descents reported......if Hammy still reads these boards he may be able to confirm/correct). The Avoiding turns were being followed by the bottom aircraft, but I seem the remember the middle aircraft (American Operator) continue the outbound hold track for a bit.