The Verge states:
Starting with Game 1 of the NBA Finals later today, Twitter cards will now support video shot with 360-degree cameras, allowing users to click and drag around the scene without leaving Twitter's app or website. The videos, which were filmed on a Samsung Gear 360 camera, will be sent out using the NBA's official Twitter account. It's unclear what the films will be comprised of exactly, but Twitter is promising "exclusive content" over the course of the series.
There's no word on when Twitter will open up its new support for 360-degree videos to other companies or individuals.