As reported by Alexander Block:

If one defines an override rule in the override.ini for an attribute that is used as an information collector, the override rule does never match. Example entry:

[ezstring_newstring]
Source=content/datatype/collect/ezstring.tpl
MatchFile=collect/newstring.tpl
Subdir=templates
Match[class_identifier]=some_class

The reason for it is located in eZObjectForwarder::templateNodeTransformation() where one can find the following piece of code
foreach ( $rootMatches as $rootMatch )
{

...
if ( $resourceNodes === false )
return false;
...
}

Here, the $rootMatches are taken from the 'matches' defined in kernel/common/eztemplateautoload.php:

...

'attribute_view_gui' => array( 'template_root' => array( 'type' => 'multi_match',
'attributes' => array( 'is_information_collector' ),
'matches' => array( array( false,
'content/datatype/view' ),
array( true,
'content/datatype/collect' ) ) ),

...

If there is no override rule for the first match ('content/datatype/view'), the second match will never be investigated due to the if statement described above.