Not sure if there is a document describing in full the migration from one to the other - but a simplified list of steps would be:
1) Make sure codec is running one of the more recent software versions (ie CE9.12.3)
2) Remove it from CUCM
3) Set up the device in your Webex Control Hub
4) Factory Reset the device
5) Follow the startup wizard to connect it to Webex
Wayne
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