My K-Line Operating Boxcar didn't work on my MTH Realtrax operating track. I bought the K-Line remote on Ebay, and it works great, anywhere on the layout.
Caution: Buy the K-Line remote. Do not buy the Williams remote, they look exactly the same, but Williams uses a different radio frequency and will not operate your K-Line Operating car.
I was so tickled with the Operating Box Car and remote, that I watched Ebay and eventually bought the K-Line Operating Coal Dump car, Operating Log Dump car, and the Operating Milk car. I can run all these cars from the one remote. I also got the milk car loading dock, so I can load and unload that car at will.
With these cars you can simulate some real railroading activity, its fun, and the K-Line cars use motors the run slowly, realisticly, and quietly unlike the Lionel Post War Operating cars.
Williams by Bachmann now makes all the above cars, and the remote.