Hi hiswmi, it is possible to change the tones and cadence but you must first know which you want to change. the settings are in the read write registers and they are documented in tc1398ed02 i think is the latest for R8.0.
page 28 (section 3.13) I_tones is what you are after.
possible Vad but I suspect the difference is that guests are uesd to external ringback tone but the tone they hear when calling internal services like reception, resturant etc is internal ringback.
Its always a hard call as each country uses different tones as you say