PANS-ATM Chapter 12 does not yield the results.
ICAO Annex 11 is not giving up its dark secrets.
Nothing leaps out of Annex 2 or 6 either, or at least as far as I can see tonight.
The exact requirements will be defined in agreed procedures between the two units, subjected to risk assessment, and published in the AD 2 section of the AIP. Well, that is where it should be, unless I have missed the correct answer in a scan of the Annexes and PANS ATM. Of course, it is not, but that is where the lawyers and investigators come in and tear it all apart afterwards.
Does anybody else remember the call of Frankfurt tower to the Brussels Tower controller etc...