It'll be interesting to see what happens when a company pisses off an employee to the point where that person creates a public repo containing all the company's AI-generated code. I guarantee what's AI-generated and what's human-written isn't called out anywhere in the code, meaning the entire codebase becomes public domain.
While the company may have recourse based on the employment agreement (which varies in enforceability by state), I doubt there'd be any on the basis of copyright.