So I am assuming you want to add these to the search results page, but this could work for any other layout handle.
Firstly you will need the layout handle in my assumption
catalogsearch_result_index is the value you need.
You then need to find the name of the block that is using the
product/list.phtml template. In my assumption it is the name
Now what you can do is using these two items of knowledge and a local.xml file in your theme simply add a new child block.
<block type="core/template" name="your-new-name" templte="path/to/your/template" />
Then in your product list template you can call
getChild to get this block. You can then set your attribute against it using
setData and then call
toHtml to get the display.
$_yourBlock = $this->getChild('your-new-name');
A slightly "nicer" way would be to use a block type that extends
Mage_Catalog_Block_Product and then you can set the product against it and call toHtml. A perfect example of this is the
getPriceHtml which takes a product object, sets an template and then calls the toHtml.
public function getPriceHtml($product)
One final and maybe simple suggestion is to simply not use a template for the single attribute and include it direct in your theme's product list.