Service Provider BU concept in Oracle Fusion

Summary:

The basic concept for Service provider model very clear that the Service provider BU provide the service on behalf of other BUs when it comes to centralize the cash collections and supplier payments but how the transactions (Supplier Payment Number and Customers Cash Receipts) are getting created in Oracle Fusion? Can someone explain this point. Here is the case -

BU1 - has suppliers Invoices and Customers Invoices

BU2 - has suppliers Invoices and Customers Invoices

Both BUs are under same legal entity and same ledger. There is common Bank account used to make supplier Invoices and collect cash from customers for the both BU.