Use an entity reference in URL as Views Contextual Filter
I have never added a views block into the admin overlay (trying to get a parameter from the URL form the views block). But this is how I would approach the problem.

In your view, pick the 'Block' display. Add a contextual filter for the field that is referencing (Vehicle). Expand 'When the filter is not available'. Pick the option PHP Code. User the following code:

return (isset($_GET['field_vehicle'])) ? $_GET['field_vehicle'] : 'all';


I am using 'all' as fallback assuming that you will show everything if a value isn't available. But I guess you can use FALSE if you want it empty.

Save it. Add the block into your overlay/admin theme. Check if it works...

Best regards.