User blog comment:Jimeee/Mounted Combat update now available on Xbox 360./@comment-5162134-20120609202338/@comment-4977109-20120610131201

There's only one Crossbow in the DLC, called "Crossbow" that's enchantable and can use different ammo ("bolts").

Source: http://www.justpushstart.com/2012/06/skyrim-dawnguard-dlc-contains-one-crossbow/