The “Common Data Dictionary (IEC CDD) published as IEC/TS 62720 by the “International Electrotechnical Commission - IEC” has specific units beyond the UN/CEFACT (for the Process Industry in particular). It is also easier to extend.
As for the UNECE a unitId (Int32) can be computed from the data identifier of the IRDI.

Working Groups - like PADIM, UAFX Motion - therefore ask to add an EngineeringUnit mapping for IEC CDD (IEC 62720). This can be in the PADIM companion spec but other information models could need that as well.