Question About Service Dgs 49228

This is a Service on Pfälzische Ludwigsbahn. A Car Transport Train at Night that can only be operated with specific Locomotives. These are the DB BR 143, BR 112, BR 218, and BR 140.

I'd like to know why did DTG isolate this one Service from all the other Frieght Service. Does Somebody know a specific reason for this?

 

I'd assume length, all these locos are shorter than the other usual freighters.

 

However, this does not explain why this one Service is set up in such a Way that it can only be used with the Locomotives mentioned above and not with the BR 185, for example.