I've seen them. They're very different from the type of load Jaeger or anyone else makes. They cover the load with two enormous sheets of clear or black plastic, one for each side of the beam. They're very loose fitting and don't have any logos or anything. Clear tends to be more common in my observations, but I know I've seen black. Maybe white too.
Jaeger Products makes a lot of wrapped lumber loads for bulkhead and centerbeam flatcars. Most of them are special order at Walthers
https://www.walthers.com/search/scale/ho-scale/manufacturer-name/jaeger-ho-products/mode/list/show/120?match=AND&q=lumber
Google 'Jaeger HO Products' to see other places that stock their products; I did not see a website for the company
George In Midcoast Maine, 'bout halfway up the Rockland branch
Forgive me if someone has already posted something like this. I'm used to seeing lumber loads on flat cars that have each "bundle" of lumber individually wrapped. I'm sure we have all seen this. Recently I've seen a couple of videos of passing trains with the lumber loads not wrapped seperately but the whole load covered with a plastic sheet. In fact I saw one myself when a train was waiting for a signal. So when the morning paper arrived I removed the plastic bag and wrapped up a lumber load (can't remember if they are Athearn or Walthers loads). Looks just like the real thing. Didn't take a picture because it was so easy to do. Anybody try this?
Jim