These remain the property of EE and are only provided on a loaned basis (gratuitous bailment) to customers taking a relevant bundle or service add-on.
Any that are for sale on second-hand marketplaces still legally remain EE property and are being improperly sold. There is a risk that EE could choose to block serial numbers which have not been returned, but there have been no known cases of this up to this point.
EE would not be required to provide any support with this equipment if you were to purchase it as it is not and cannot be registered to your account.
