A shortline company refers to a company making a limited line of products, compared to companies such as Deere, Kubota, and others who offer a full line of tractors, riding mowers, industrial and road equipment. Usually these shortline companies will off implements but not tractors.
A few to check out would be the Frontier, Leinbach, LandPride and Durograder, to name a few. Some are available with scarifier teeth too similar to a boxblade setup.
Here is a pic of my lawn that I smoothed up with the landplane in the above post.