This is a reply received after emailing to [email protected], which is the official firebase support email after gogle acquired firebase in late 2014.
From: [email protected]
In order to transfer ownership of a Firebase instance, we need you to do two things: add the new owner as a collaborator; then, fill in the form below and email it to us as written verification. This must be sent from the email address which owns the Firebase instance.
-----------------
REQUEST TO TRANSFER OWNERSHIP
I authorize the Firebase team to make **<new owner’s email>** the owner of https://**<firebase instance>**.firebaseio.com effective immediately. I have added **<new owner’s email>** as a collaborator to verify the email address is correct and to certify that I am the current owner. I understand that I am effectively granting **<new owner’s email>** full read and write access to all stored data for this instance.
-----------------
This is from an answer made on stackoverflow by the user Qwerty