PCDev has confirmed on Twitter that they do not have plans to support cross-platform play between Windows 10 on PC and the Xbox One platform for Call of Duty: Black Ops 3. Windows 10 is set to launch on July 29th and one of the features it includes is the ability to have cross platform play with Xbox One if developers support; one of the first titles to announce support is Fable Legends, but it seems that Call of Duty: Black Ops 3 will not be supporting this new feature.
@Btravis1177 We have no plans to support cross-platform play at this time.
— pcdev (@pcdev) July 18, 2015
Treyarch has already confirmed beforehand that Call of Duty: Black Ops 3 will be compatible with Windows 10 OS, but it seems all of it’s functionality will be limited to Steam, rather than the Xbox app on Windows 10. Another big feature of Windows 10 is cross buy between PC and Xbox One titles, but as of now, there’s no indication from Activision or Treyarch if that will be supported for Call of Duty: Black Ops 3.