Does implementing MBCx remove the requirement for discrete OCx functional performance testing?

The discrete functional performance testing must be included in the ongoing commissioning plan regardless of whether the project pursues monitoring based commissioning as well. In the context of LEED, the MBCx plan leverages data from meters and equipment sensors to assess energy performance and system functionality in a continuous fashion but it does not negate the need and benefit of conducting test procedures with a team onsite to exercise the equipment and verify that it functions according to design intent under varying conditions.

There is a good description of this in the reference guide under Further Explanation - Monitoring Based Commissioning Basics.

Ben is correct. The way I think of the MBCx is helping design a way for an owner to quickly see on an on-going basis if the system is performing as intended and tested during the functional testing. Well designed trends and alarms can go a long way to helping a system to perform better over the long term.