\version "2.19.82"

\layout {
  \context {
    \name "MarkLine"
    \type "Engraver_group"
    \consists Output_property_engraver
    \consists Axis_group_engraver
    \consists Mark_engraver
  }
  \context {
    \Score
    \remove Mark_engraver
    \accepts MarkLine
  }
}

aux = {
  s1*2
}
marks = {
  s1
  \mark\default
  s
}
soprano = \relative {
  s1
  \break
  s
}

<<
  \new MarkLine \marks

  \new StaffGroup <<
    \new Staff \new Voice \soprano
    \new Staff \new Voice \aux
  >>
>>