I ran into a little issue the other day configuring vcloud director. I wanted to remove an organization VDC completely. Lets Call it vDC-To-Be-Deleted. Of course to do this you must disable the VDC and remove all of it's resources (networks, templates, and vApps).
Upon trying to remove the networks I kept getting the error vDC.... cannot be deleted, because it is in use...
The edge gateway is used by an other vDC but visble in the vDC-To-Be-Deleted. I thought when removing the vDC-To-Be-Deleted, the EG will just move to the other vDC, since it will be used within the organisation and without sharing it explicitly (like networks).
I too changed recently the ownership of one vDC Networks in order to delete the vDC.
So it seems like it's a database change as well..