It sounds like a fairly straight forward use of alfresco document management. You can associate the images with meta data about the image, do workflow, search, manage permissions for each business unit etc. There's also a host of other features that may be useful such as version control, image transformation, thumbnailing, tagging etc. And there's also an image management module you should take a look at.
And as you have seen on the wiki there are OCR plug ins if and when you need them.
You can have a several separate instances of Alfresco for unit or one big one, Alfresco will comfortably handle a few million documents so I'd start with a single instance.