Can a shared People list or a Home dashboard widget give someone visibility into Registrations data without granting them Registrations access?

Answer

Both a shared list (via list-collaboration) and a shared Home dashboard widget can let a person without Registrations access see registration data, since collaborators on a shared list or dashboard can view results regardless of their own product permissions — but lists only cover the specific condition built in, and Registrations widgets only show recent/aggregate activity, not a person-specific on-demand lookup.