for Nova CEWS to other Nova CEWS? Yes, it was written into their original rules (Wars of Reaving or the Supplemental, I forget which).
For C3I? No. Those networked units are "locked in" until the game/match ends.
Should have been in the errata a few years ago; been a while since I had to look it up (it's not often we play Homeworlds in my neck of the woods)