A creditor is not allowed to delete an accurate credit listing, even if it is subsequently paid. It can be shown as paid, but it should not be deleted, unless it should never have been posted.
Why? Are you talking about agreements between the CRA's and the Original Creditor and/or Collection Agency which stipulate accurate entries are not to be removed?
A creditor can delete an account if it's paid just as they can update it if it's not. There is NO LAW that says a creditor must report at all and there is certainly no law against a creditor deleting a paid collection.