I agree that the importance of IT systems, architecture and involving the department early is critical to a successful integration. IT systems tend to touch on every aspect of the business/functional workstreams and create interdependencies. Having an IT workstream with a dedicated lead from both parties and recognizing early on that IT should be involved early is sound planning for integration. I once participated in a 6 hour marathon session led by the IT Architect engineer planning for cutover and how the IT architecture needed to be set-up. I am not an IT person, so I can’t elaborate, but it certainly demonstrated the importance of not overlooking IT.