How are you creating the employee BP's in your revised system? ECC HR integration? or manually creating the employee BUP003 record?
Per note 996789 there are some various programs you can load. We used report ZHTTMH_CP_B207_BP_RESTORE as we had some employees obtain a new ECC pernr and we wanted to assign them back to their original BP # in CRM.
Looking at table HRP1000 & HRP1001 to see how the BP, user, is tied to the CP central person and which positions & org units will help you in understanding why the belong to me does not work for these id's.
Regards,
Glenn