Well… it would appear as if my inference was wrong. The licenses is associated to the Account and not the device.
Looks like the person you shared the device with would need to purchase a CAM plus license as you identified.
From a utility/architectural perspective that makes since in terms of how the license is structured in the app, as in you purchase with your primary account, you are sharing with a different account, and can move from one device to another but…logically, I am still of the mind set that if a Cam plus License is applied to a device those attributes should pass along to the person you are sharing with.
There is a wish list item for this functionality. While this relates to the Person Detection there was also a CAM plus Wishlist item that got linked to the original. Check it out ang give it a VOTE. on the top left of the page