Note that this pertains only to allowing applications to provide FAC or CMC for calls they may be attempting - there is no facility for an app to learn of any FAC or CMC used during a call they may be receiving.
Applications can determine the FAC or CMC used for a particular call historically via the Call Detail Record system:
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: