While I am not sure of the full context of your question, there is a general principle that helps in achieving buy-in in most circumstances. One of the best motivators in effecting change in others is to show them how the change will benefit them. Does it all them to do more work in parallel? Does it speed up individual requests? If you can see things from the other group's perspective, you can find the mutual benefits. However, if you are at a loss to identify how they will benefit, perhaps you could spend some time learning more about their work. As the pace of IT struggles to keep up with business demand, most professionals have far more on their to-do list than they can ever hope to get done.
One other area to watch out for is local optimization. Because of the reasons stated above, many teams unknowingly make the enterprise move slower by purely optimizing their own tasks. This is a much more difficult problem to deal with. Your task here is to convince people to change for the greater good. If your organization operates in deep silos, this will be quite a challenge indeed. It may even be the case that the goals against which the group is evalated drive or reward local optimizations. You will need help from your leader (and perhaps multiple levels of leadership) to effect change here.
The key in any situation is to spend time with those from whom you need buy-in. Understand how your proposal benefits them, and also watch for entrenched silos that are barriers to your change.
