Push Notification subscribers must opt-in and actually choose to receive the notifications.  

An import/export of subscriber information would bypass this opt-in and allow push notifications without approval. Additionally, since users are added on the basis of their browser, and not their email address as with traditional email marketing autoresponders, we are provided a browser key when a user subscribes which acts as their subscriber ID. 

That browser key will only work via Push Subscribe, and hence - we cannot support imports or exports.