OK, I broke down and asked Meraki support since the customer was pushing for this information in advance of deploying CA licenses.
According to support, the upshot is this:
- you can move CA licenses between cameras; or more precisely, you can remove a CA license from a camera and it's returned to the license pool -- you can then assign it to another camera
- when you remove the CA license from a camera, all of the cloud footage stored is lost; on camera footage remains unaffected