Yes, Output Ground Common (SCOM in DB-25 & COM in screw terminal blocks) is the same as Power Ground Common (COM in Main Power & Alternate Power screw terminal blocks).
This is true for 8BP01, 8BP02, 8BP04, 8BP08, and 8BP16.
KEYWORDS/PHRASES: SCOM, COM, 8BP01, 8BP02, 8BP04, 8BP08, 8BP16, common, signal common