A select number of Pokémon GO players have begun receiving Exclusive Raid Passes to catch ultra-rare Pokémon, such as Mewtwo. There’s currently no word on when they will be rolle join a special Raid Battle. You can use this particular pass only at a specifiedd out to all players, but stay tuned for any updates. An Exclusive Raid Pass is a special in-game item that enables you to limited-time event. To see how the Exclusive Raid Pass looks, click here. If you’re not invited to join an Exclusive Raid, you’ll be met with the above screenshot.
Source: Andrew Goldfarb
Pokémon Blog 