What you described is a quite common role of QA automation team, but it does not really replace TDD. Separate team working on a test can do it only relying on a remote contract (e.g. API, UI or database schema), they cannot test local contracts like a public interface of a class, because that would require the that code already to be written. In TDD you often write the code AND the test at the same time, integrating the test and the code in compile time.