Frederik
If you have the Linework on a Layer or Layers or you have the IFC Data on a Layer or Layers you can set the Display Priority in Layer Manager and push the IFC Data to Background (From Normal) or pull the Linework to Foreground (From Normal) using the display priority settings. In my test I had the Red line on Layer 0 and the IFC data on other Layers and when I set Layer 0 to Foreground it pulls it from behind the IFC Data to In Front of the IFC Data. However even though that works in Plan View it does not appear to work in Sheet View - so you are right this is an issue and I will log it in today. I also saw another issue at the same time so thanks for raising this. Apologies - the Geospatial Team did the IFC changes in the 5.1 release and I have not tested or validated the Plotting workflow since they made those changes.
I also tried your Copy process, and it does seem that copied IFC objects do not get picked up in the Dynaviews for Plotting - again I reproduced and have reported in the issue and will let you know the outcome when I hear back.
Alan