The Planner preview is available to First Release customers who have Office 365 Enterprise E1, Office 365 Enterprise E3, Office 365 Enterprise E4, Office 365 Enterprise E5, Office 365 Education, Office 365 Education E3, Office 365 Education E4, Office 365 Business Essentials and Office 365 Business Premium. In order to get the Planner preview, IT administrators of those applicable need to set it up.
For those wondering how Planner will integrate with Office 365 Groups, each new plan created in Planner automatically creates a new Office 365 groups. And every pre-existing Office 365 Group will get an associated plan.
Microsoft announced recently it was adding more services to its First Release program, which allows companies to designate certain people to get new updates earlier than the rest for testing purposes.