getting repeat bar lines to print across an entire system

[Robert Edge]

hey there,

So this:

\score{

  \new StaffGroup <<

    \new Staff {
      \bar ".|:" c'1 c'1 \bar ":..:" c'1 c'1 \bar ":|."
    }

    \new Staff {
      \bar ".|:" c'1 c'1 \bar ":..:" c'1 c'1 \bar ":|."
    }

  >>
}

does what I would expect to do, the repeat bar lines are drawn across the
entire system.

This, however, does not:

\score{

  \new StaffGroup <<

    \new Staff {
      \bar "[|:" c'1 c'1 \bar ":|][|:" c'1 c'1 \bar ":|]"
    }

    \new Staff {
      \bar "[|:" c'1 c'1 \bar ":|][|:" c'1 c'1 \bar ":|]"
    }

  >>
}

The repeat bar lines break at each staff.

How do I get the second style repeat bar lines to behave like the first?  I
want the little doo-dads and I also want a continuous line across the entire
system.

I am using Lilypond 2.18.2 on Fedora 20 (planetCCRMA).

thanks!