I found this on the web. It contains a list of available Roco replacement boxes in assorted sizes.
This means that you can replace the Fleischmann type plastic boxes with the traditional cardboard and styrofoam ones, albeit generic ones and vice-versa.

http://www.roco.cc/uploa..._Verpackungsgroessen.pdf

I may order a few for coaches, since it would be nice to be able to store new and older Roco items together and the different box types don't stack well.

Regards

Mike C