Eligible CxA for Design&Built project

It all depends on the situation. The owner can always provide their own fundamental and enhanced commissioning, as long as they have qualified people who have the requisite experience. So if your owner is building the project for themselves, and they happen to be constructing it too, then yes, they can be the CxA. However, if you have a design builder that is building for someone else, or a build to suit, or lease back, or other situation where the owner is not occupying the building, then it becomes very murky in my mind. Clearly the intent is to have someone who is not involved in the design process for fundamental, and someone not associated at all with the contractor for enhanced.