Ok, I found a workaround, but it’s thrown up another problem, see here
To create multiple tracks in a project, or rather load a series from another project, record a short burst of audio on all the tracks which you want to transfer from the first project.
Select all the audio parts, and Copy them using CMD/CNTRL-C
Open the new project, don’t select any of the existing audio tracks.
CMD/CNTRL-V to paste in the audio parts, and Cubase creates a new track for each, named after the audio part (which were named after the tracks in the first project)
Delete the audio.
You still have to do all the routing, and as I discovered this is more tedious than it needs to be because it appears the multiple track routing function in C6 is broken.
Still, it’s a start.