I'm sorry, but I feel that some facts need to be injected to this discussion:

The algorithm for calculating IMEI checksum is public, so anyone can make up valid numbers, no need to find a number of another phone.

If you change your device's IMEI, you are better off using an invented number than a number of another phone. If you use a number of another phone and it is reported stolen, your device will be blocked. No chance of that with an invented number.

Some networks (those in South Korea, for example) use IMEI white lists for allowing phones on the network, so you do need a valid number from a phone that is on the list, but a list from Nokia does not help anyone in that regard.