Possibly, I'm not understanding the code in efq_views.views.inc that allows remote entities to override Views handlers... But I don't think it's working?

In any event, there should be some sanity checking. To my knowledge, it's not a requirement to define property info for each remote entity property.

// To add support for custom handlers, we need to know if the property is
// local or remote.  In the latter case, the property info is stored elsewhere.
if (isset($property_info['remote_property'])) {
  $property_info = $metadata['properties']['entity_data']['property info'][$property];
}

Should at least check...

if (isset($property_info['remote_property']) && isset($metadata['properties']['entity_data']['property info'][$property])) {
  $property_info = $metadata['properties']['entity_data']['property info'][$property];
}

But also, I don't think that's what's meant to be returned. May need to be...

$property_info = $metadata['properties'][$property]['property info'];

I'm not familiar enough with Remote Entity to know for sure on that, though.