Chaps(& Chapesses): I wonder of you indulge me? Is the ICAO publication "
Phraseology Reference Guide" the definitive guide used by nation states to base their own ATC procedures upon or is there another guide. I'm particularly looking looking for guidance regarding the legitimacy or otherwise as the issuance of unsolicited taxi clearances. Such a clearance might be given when a ground controller sees aircraft is in a position to taxi, has not requested a clearance, but to help things along gives a clearance like "Bigjet 123, when ready taxi to holding alpha and hold short." It's the source documents which I'm particularly interested in.
Replies gratefully received via the normal channels,