I ran into problems with using RulesAction "Fetch entity by property" for file entities: my component didn't appear among available VBO operations. The reason was failing access check which returned
$op = 'view' and
$entity_type = 'file'.
entity_metadata_file_access($op, $file = NULL, $account = NULL, $entity_type) responsible for this does so because no $file object is given.
Steps to reproduce:
1. Create an Action Set component with a parameter of type Entity = say "Node", then add action "Fetch entity by property", set Entity Type = "File" and property say filename = anything.
2. Now enable this component in VBO field of a view which lists Nodes.
3. Visit view page - the operation added doesn't appear in the operations list.