I will answer this from the legal perspective in Canada, however, the IP laws between Canada and the US are substantially very similar, so I would venture a bit out on the limb and say it is applicable. This applies whether the device in question is a mobile device, laptop, or desktop.
If an employee is using a device they have legal ownership over for storing or producing work for an organization, that work product legally belongs to the employee. UNLESS, the organization has had the employee sign a waiver stating the contrary AND the organization has made sufficient and reasonable provisions to electronically segregate organizational material and personal material on the device and to remove said material and segregation when the employee leaves the organization.
So, think from the perspective of an iPad or phone or whatever, the organization installs something like MobileIron to create that segregation and then has the employee sign a waiver accepting that they have no rights whatsoever to any organization IP/work product produced or interacted with on that device.