The CID of a SD card is most certainly permanent and not changeable. Garmin relies on that when they sell maps on SD and microSD cards.
If a map is unlocked with a key using a UnitID it will only be unlocked for that specific unit. If the unlock key is based on a memory card CID the map should be unlocked by using it with any Garmin GPS capable of reading the specific unique memory card. Trying to copy the map from one memory card to another needs another unlock key based on the new CID for the second memory card.

All this can be avoided by removing the lock mechanism with "Garmin unlocker" if that's more desirable.