The only real study done (published, peer reviewed) showed that if you drink 4 cups of tea every day, you can lose up to 8 pounds over the course of a whole year. The truth isn't as impressive as the marketing
The Wu-Yi tea is the same thing as regular oolong tea, it's just another word for it. There are plenty of legitimate tea companies that sell this type of tea at regular prices, without the hefty markup that comes with the claims.
Personally, I find that drinking tea is soothing and satisfies my cravings for comfort, so I'm less likely to reach for something with calories. I think that's the best way tea can be used to help weight control. That's just my personal opinion