As Shan suggested P_ORGXX would be the way to go, as it is based on administrators in IT 1 valid at the time of access.
P_ORGIN does not use administrators.
see links
P_ORGXX (HR: Master Data – Extended Check) - Authorizations for Human Resources - SAP Library
Further, re: your system build/config, what is puzzling is
a)Payroll area: On what basis is this organized or set up? Even if the organization is decentralized, it is not required to have one payroll area for an org unit or ESG.
Refer to the help info enclosed or other info re: Payroll areas and the links below
b)Org unit & ESG default: The Org unit is determined when you assign a position to a person. EG & ESG's can be defaulted based on the Org unit's EG/ESG infotype HRP1013, provided you have configured T777I to maintain 1013 for an OU (object type O).