How would teams use it to distribute and share their own modules and applications within the organization?
I wouldn't have it based on CPAN. For code written inside the organisation, I'd use a source control system. Deployment, I'd either distribute using the source control system, or a package system that's appropriate for the OS (for instance, rpms + yum + cfengine) and the organization. And I'd use the same package system to distribute external packages.
Frankly, I wouldn't know what to use a "private CPAN" for. What's the point, and why would an organization want to limit itself to a system that's geared to a single language, and is designed to do quite different things than corporations need?