If you want to be precise, the separation 'standard' is NOT 1NM...I suggest you read MATS.
This is more-or-less off topic, but you will only find the 1 NM stuff in the Orstralian MATS
AFAIK, the ICAO standard is based on the probability model, Oz complies with stuff like the cross-track tables, doesn't with that magic 1 NM. And I agree, all bets are off in the TIBA.