That could be a mechanic, but I do not think that (if this was ever going to be considered, which I doubt) relying totally on Tiberium based deaths would be the answer.
I suggest that it would be a very gradual process, that becomes stronger over time with more enemies and more advanced ones as well. Basically a way to break sieges and counteract snowballing by having an outside influence. I do imagine that you are able to shut down the Tiberium stuff, perhaps by destroying a giant crystal that is hidden somewhere in the AI “base”. Or destroy all of those tree things that spawn to stop their growth.