When you Add a Reservation in a specific facility, and there is an existing reservation in that facility for the same time, your site will trigger a response that says there is a conflict. This response will give you the option to Proceed with the Reservation if you have permissions to the facility. This works for both single events and recurring events.
For Recurring Reservations, there must be at least one available day in the facility during the timespan of the recurrence. If there is not a single available time slot, your site will display a message and will not allow you to proceed with the reservation.