I have an ex-TPE "D" class ticket to SIN. I have used the outbound and wanted to cancel the in-bound sectors. Fare basis is D6MIB.
I called CX office to check and was told that there is no refund value for this partially used ticket except the fuel surcharges & taxes paid for the in-bound sector only. Will suggest that you give a call to CX Taipei office to check it out.