Companies don't make programmes, people do, and if those people are the same people who used to work for Westcountry then they will know when the anniversaries are.
Companies are groups of people, and the culture of a company comes from the top down. The difference between Westcountry circa 1993, and Westcountry circa 2001, was a massive culture change that came when Carlton Communications bought them in 1996. That whole story by the way is weird enough, with Carlton actually being treated as a white knight in a battle between GWR (the old radio company) and United News & Media, who owned neighbouring HTV. But yeah, the company that existed in 2001, was way different from the original company that launched on screen in 1993.