At Active Voice, there was a requirement to be a Unity Certified Engineer to install and support a Unified Messaging system; and a Unity Certified Technician to install and support a Voice Mail only System. This was put in place to ensure the success of every deployment. At Cisco, there are no processes in place to verify certification for each system sold and when contacting TAC for support.
At Cisco, when a system is sold, there is a cursory check for certification, and if no one is certified, there is a recommendation to either go through Professional Services or another reseller who has certified individuals.
The most important thing to take away from this discussion is how successful each installation will be. If someone is installing Unity is not intimately familiar with how Unity works and with the back end components that interact with Unity, the customer will probably be dissatisfied with the solution.
Unity is not something that someone can learn on the fly. Installing a Unified Messaging solution is not something that can be done successfully without appropriate training and experience.
