How data flows between SAP and Ariba for punch out catalogs, when we have both POIA and APC for the same supplier.

I would like to know how the data flows between different systems when we do a Punch Out catalog transaction for a particular supplier. We are using Ariba P2P,APC and Ariba POIA modules. For normal PO transaction happens between SAP and Ariba network via EDI.

But I would like to know how the transaction will happen if we are using both APC and POIA and we shop via punch out catalog.