When you set up a new branch/plant, this functionality eliminates the need of manually setting up new bills of materials from start. The Copy Bill of Material by Branch/Plant program (R3002CPY) can be run in a Proof or Final mode. In both the modes, the program creates reports. The report edits items against the Item Branch (F4102) table and adds item records to the file if the item records do not already exist. The report lists the bill of material and items created during the process. When you run the program in the Final mode, the program updates all the necessary data in the Item Branch (F4102) table and Bill of Material Master (F3002) table.
Additional documentation can be found at JD Edwards EnterpriseOne Applications Product Data Management Implementation Guide section 4.5.5 Understanding the Copy Bill of Material by Branch/Plant.