To report on the work group you will require a calculation such as the example below:
CTBI_GET_WORK_GROUP_CODE(P_EMPNO=>PRCI_HR_PERSON_MASTER.PERSON_REFERENCE)
Then filter the output of the report as required based off specifications.
If a custom report is required it will require the attention of Optimization Services which can be reviewed here.
Also review how to build a smart calculation here.