There is no built-in support for Exporting/Importing ReservationInstances, but you can use an automation script like Gelber mentioned. ReservationInstance (and many other classes) have a "ToJson" & "FromJson" method implemented which can be used to export/import all the relevant data for that object.

Beware though that ReservationInstances have references to Resources and other objects, which might not exist on the system where you're importing them.