Jet,
I used to fly GIVs in Germany. I can't reference PANS-OPS, but Chapter 18 of AFI 11-217, Vol 1, does give some excellent guidance on ICAO and PANS-OPS/SARPS, and how procedures differ from FAA procedures.

Technically, there are no procedure turns in ICAO--just reversal maneuvers. They are designed to be flown exactly as depicted (like procedure tracks). Reversals may be defined by crossing radial, DME, or timing to remain w/in a certain distance. So the short answer of when to turn inbound is "it depends".