Can a Business Unit raise POs itself and also utilize a Central Shared Procurement Business Unit?

Is it possible to configure a Business Unit that does Procurement on behalf of itself sometimes but also utilizes the central shared procurement business unit?

For example:

1. Business Unit 1

2. Central Procurement Business Unit

Business Unit 1 would like to create Requisitions that turn into POs for the BU 1 Procurement Business Unit sometimes. But it would also like to sometimes create Requisitions that turn into POs via the Central Procurement Business Unit.