My experience in acquisitions is predominantly using the absorption model. Over time, we moved towards a properly resourced Integration Management Office, but I would still consider it to be lightly staffed. Operations teams know they will ultimately be responsible for the new acquisition, so their desire is to be involved as early as possible. It takes intentional leadership to hold everyone accountable to their established roles. I found that having operations involved in key decisions in the integration plan, alleviated some of their concerns. I think the real turning point for us was when we installed a trusted operations leader (temporary assignment) into the target company on day 1. This operations leader worked alongside the integration lead to execute the integration plan. We designed checkpoints at which the operations team took on certain responsibilities.
In summary, I don’t think transferring responsibility for integration management is a “switch flip”. It can be a staged process. Assigning a trusted operations leader to work within the target company on day 1 was key for us.