Hi,
Once provisioned, custom IP prefix ranges can't be moved to another subscription. Custom IP address prefix ranges can't be moved within resource groups in a single subscription. It is possible to derive a public IP prefix from a custom IP prefix in another subscription with the proper permissions as described:
https://learn.microsoft.com/en-us/azure/virtual-network/ip-services/manage-custom-ip-address-prefix#permissions
Reference: https://learn.microsoft.com/en-us/azure/virtual-network/ip-services/custom-ip-address-prefix
Regards,
Karthik Srinivas