No, for security & legal reasons.
This is also something that i need - desperately. I understand there is no such feature in general, but if there is a way we can prove we are the owners of the key (by giving out account info, pwd and key pwd) would that be doable?
No (and what you suggest would be no guarantee of ownership). Adobe PGB makes clear that they do not allow downloads of the signing key, and they are correct in this regard. It is far too much of a liability issue from a legal standpoint, and would be extremely insecure (what if someone compromised your account, for example).
You should never rely on PGB as the only holder of the key. You must always maintain a backup of your key yourself -- in fact, ideally, you'd maintain several backups -- at least one locally, at least one in a remote location (that you trust), etc.