Gregorian Divisiones

[Dan Eble]

Is there an ancient music expert lurking who is willing to clarify a couple of 
things about divisiones for me?

The LilyPond Notation Reference says, "A divisio . . . is a staff context 
symbol that is used to indicate the phrase and section structure of Gregorian 
music."  I see that these are implemented as breathing signs, which makes sense 
except that LilyPond engraves them in voice context.  Which one is it, staff or 
voice?  Or doesn't it matter?  Is this notation ever used with more than once 
voice per staff?  It is ever used for polyphonic music at all?

The NR also describes a "finalis" in the same section.  Is a finalis as much 
like a breathing sign as the divisiones are, or is it more appropriate to 
consider a finalis the ancient equivalent of modern section and final bar lines?

Thanks,
--
Dan