Depends mainly on the analog adapter and the PABX itself.
I can tell you I have a little gateway (like a little-mini-micro PABX for a very specific purpose) and my Beocom 3 and Beocom 1 phones get caller IDs when they ring on calls coming from the gateway. However, this happens only insofar as the gateway itself sends the correct signals.
Bottom line, Beo will display Caller ID if whoever is sending the ringtone sends the correct signal with the correct timing in the correct protocol for the phone model. Various Beocoms sold in various countries are generally sold to meet the protocol standard of the country of sale.