As someone who used to be in Hashgacha I will try to translate: Case by case basis can mean any of the following:
A) We have yet to find a case that it is unapproved but we are keeping our options open
B) we have yet to find a case that is approved but don't want to get sued or harassed
C) we have valid reason for case by case e.g. we know the Rov Hamachshir is knowledgeable, so if its in a service area where he is visiting himself (near where he lives) we trust him, however if its across the country from him and hes outsourcing we don't necessarily trust the people he outsources to. Or maybe they are trusted for certain things but maybe not flavoring companies since that is more complex etc....
As far as the K.O.A. IMHO it would be more a case of the middle one