This person or team will work with the Integration Engineer to work through problems with the interface and troubleshoot them. Depending on how high-level the problem is there may be different levels to Support.
One of the ideas that comes up in the discussion is the fact that it often makes sense to divide support activities up by the type and level of complexity. So one might choose to have one tier of more skilled group that can support interfaces which is different from the normal customer support group.
This is idea of separation of concerns.