All other buildings should be included in OP 3: Building Operations and Maintenance. That credit awards points, in part, based on percentage of space that is certified under LEED O+M.
A new building that is certified under LEED BD+C (or another rating system for new construction and renovation) does not continue to earn points on that basis forever. Once a building is more than 5 years old that space should be moved to OP 3: Building Operations & Maintenance and excluded from OP 4. It will only continue to earn points for LEED certification if it is certified under LEED O+M.
Please note that the two credits are generally mutually exclusive. Buildings space that is reported for OP 3 should typically be excluded from OP 4 and vice versa.