ChoirStaff with spanning bar lines at breaks

[Jeff Olson]

I'm transcribing an SA-TB piece with lyrics between the two staves and 
using a ChoirStaff so there are no spanning bar lines between the staves 
that would interfere with the lyrics.  But my source does add spanning 
bar lines at the end of each system.

How can I get bar lines in a ChoirStaff to span staves only at the end 
of each system?

See attached MWE-ChoirStaff-end-bars.ly

Jeff

MWE-ChoirStaff-end-bars.ly
Description: Text Data