You definitely can do a Local Refinement following symmetry expansion! This will be similar to, but not exactly the same as, enforcing symmetry on unexpanded particles. I discuss the difference a bit in this post.
If you perform a local refinement of symmetry expanded particles, it is similar to but not the same as performing a global refinement enforcing C2 symmetry. This is because when you enforce C2 symmetry, you force the map to be symmetric. When you perform a refinement, typically one of the two subunits will align better than the other. This is especially true if the subunits are flexible. In this case, half of your map would be of higher quality than the other, since the particles are all aligning there. This results in a map with a higher-quality A and a lower-quality B.
If you have any other questions about the process please let me know!