Asset Books and MOAC in R12

I may be asking a question that has been asked before but I'm new to Assets and can't find a satisfactory answer anywhere on the Oracle Support website. We operate a complex (90 entities) multi-org multi-currency environment with each legal entity having its own asset book. We also operate a Payables shared service centre. In 11.5.10 the payables users had an individual payables responsibility per OU so when they transferred assets from Payables all the invoices that were in an OU were transferred to the Asset Book specified in the concurrent program (Mass Additions Create) parameters. With the introduction of