Ok, I understand this better. In the next major release, the downstream team is delivering a new feature, the Procurement Workbench, that will allow for the aggregation of PRs and send to Ariba Sourcing. It will create a Sourcing Request which can be routed to the appropriate sourcing manager to conduct the project. The results would be sent back to downstream for the PR to be approved. After that, I am not fully versed on the downstream's integration capabilities, but I think they could then send to SRM.
David Morel