My understanding...and this is what I have HEARD, not what I have experienced...is that LLA only applies to radios that have the LLA option.
In Motorola speak, it's called radio authentication. Only a radio that HAS the radio authentication feature can use radio authentication. A radio that does not have this feature can still listen without being an authorized subscriber radio if it is correctly programmed.
But if it has the LLA feature, then it can't hear the system if it's not authenticated.
Since P25 standards are the same for any vendor, it would seem likely that LLA behaves in the same manner as radio authentication.
A Harris vendor should be able to delete the LLA option from your radio for a small price. Usually people buy features to ADD, but features can be deleted, too.