Content referencing the referenced content
I don't see any problem here. or any difficulties to do this.. You only need a block with services of certain company, so you can create a views block , pass company id as argument (by contexual filter), and exclude current service from it.. But, I don't think that simply assigning it to region can help you, because you will need to fetch company id from service page and pass it to view block. I think the solution will be to implement hook_block_info and hook_block_view hooks to create another block and fetch company id from service page and display it.. 

example:

function MYMODULE_block_view($delta = '') {
  $block = array();

  switch ($delta) {
    case 'company_service':
        // there is multiple ways to get field value from entity. In this example I am it getting with entity_metadata_wrapper function from Entity API:

        $service_node = menu_get_object();
        $service_wrapper = entity_metadata_wrapper('node', $service_node);

        $company_id = $service_wrapper-&gt;field_company-&gt;value(); // I don't know the structure of your entity fields, that's why we assume that $service_wrapper-&gt;field_company-&gt;value() will get company_id..

        $block['subject'] = t('Company services');
        $block['content'] = views_embed_view(VIEW_NAME, DISPLAY, $company_id);
      break;
  }
  return $block;
}