Bing has published a new post on their webmaster blog which outlines the various mobile bots they use to crawl your sites along with a few mobile recommendations. For starters Bing makes it a point to mention the benefit of responsive design vs separate mobile website versions. Actually Bing has been preaching this since 2012.
Furthermore Bing has also added a few new crawler varients to include some of the more popular mobile device types, such as:
Mozilla/5.0 (iPhone; CPU iPhone OS 7_0 like Mac OS X) AppleWebKit/537.51.1 (KHTML, like Gecko) Version/7.0 Mobile/11A465 Safari/9537.53 BingPreview/1.0b
Mozilla/5.0 (Windows Phone 8.1; ARM; Trident/7.0; Touch; rv:11.0; IEMobile/11.0; NOKIA; Lumia 530) like Gecko BingPreview/1.0b
Mozilla/5.0 (iPhone; CPU iPhone OS 7_0 like Mac OS X) AppleWebKit/537.51.1 (KHTML, like Gecko) Version/7.0 Mobile/11A465 Safari/9537.53 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)