We have not seen any DevNet activity (onboarding/doc publishing requests, etc.) from the UCM Cloud team AFAIK, so I'm not 100% sure, but based on the product description - 'Cisco UCM Cloud has all the features and functionality of Cisco’s Unified Communications Manager' - I would venture that all the usual APIs are there, similar to the situation with HCS.
Reaching out to some contacts in that area who may know more about the specifics and any API/developer caveats between CUCM on-prem/HCS/Cloud...
