Yes, it will be possible to just call an alternate version of the file for your category. I'll have to take a look at which file will be the appropriate location for the alternate call.

You might also consider the approach taken by the Column Layout Grid mod, which has code for both the standard "rows" product listing and the "columns" layout, switching to use different parts of the file as appropriate. That keeps all of the modifications in one file. Actually, what you want to do will probably be best served by modifying product_listing.php and tpl_modules_product_listing.php, just as Column Grid does. Download that mod and look at it to see how it works.