Would a proposal that is only relevant to Engineering B, but will enhance two separate Engineering departments be multidisciplinary?
For Engineering, if the department submits in Engineering A, to be a multi proposal the partnering department must be outside of Engineering A. If a department under Engineering A partners with a department from Engineering B, then it can be considered Multi. If two Eng A or two Eng B departments submit a proposal together, and they are separate units with separate administrations, then they are welcome to format their proposal the way you would with a Multi proposal. As in, they should probably submit two mission statements that explain how the project addresses priorities in each separate department. But, like I said before, the Multi label is just a guideline, if they write it that way then it will be easy to set up the review for it, but labeling Multi will not change how it competes, because it is a single competition.