R12.1.3 - To use Blanket Purchase Agreements, do Encumbrances need to be turned on

 We are currently in the process of upgrading from 11.5.10 to 12.1.3 and need to make a decision on whether to implement a seperate operating unit for each government ministry or not. One of the key factors in this decision is whether or not encumbrances will be needed for Global BPAs to work correctly in a seperate OU setup. 

Could someone please fill me in on the Global BPA procedures and requirements in 12.1.3.

Thanks,

Dan