Quick question for the non-controllers on this thread, do you know what LOSA is? By definition there was no loss of separation, so any discussion of avoiding action is moot. Secondly, ICAO has no relevance because LOSA is a purely ASA invention. No other ANSP has SA, so there can be no LOSA.
All BOS/LOSA events are investigated by ASA because the first thing that happens is the controller/s is/are suspended. The awkward truth is that as often as not it was simply a case of controller or crew error. Sometimes there just aren't any systemic issues (not the case for the OOL BOS by the sound of it though).