System breaks in imported Musix-Xml

Yesterday i got an Music-xml-Export from a friend. (He uses capella) He made some manual System Breaks, which are kind of static after importing. At every spot he did this, I can see a Clef and a time signature which are BTW undeletatble...Is that .mxl import behaviour "by design" or a bug. (or is the export of capella not standard-conform)? Onfortunately I mustn't send this file to you without asking him for permission to do so. Any ideas?