Question about managing two Marketing Cloud Engagement tenants

The client currently has Tenant A and is planning to acquire a separate Tenant B.

Is there any way to centrally manage Tenant B from Tenant A?  

For example, can users access or manage Journeys, Automations, Data Extensions, or other components of Tenant B while logged into Tenant A?

Or, since they are separate tenants, must each tenant always be accessed, configured, and managed independently?