Content in custom post types that exist in the current site will be selectively migrated, adapted, or abandoned as appropriate.
Every media file uploaded to WordPress is represented as an Attachment. NAPCS wants to keep some of these, and is free to delete unwanted files from the current site at any time. The desired files and related metadata will be selectively migrated, either by some size/age/type criteria, or according to a white- or black- list provided by NAPCS, or some combination. More discussion is needed.