I found a review of the Cross score here:
Reviewed Work: Messe de Nostre Dame [For] Mixed Voices by Guillaume de Machaut, Lucy E. Cross
Review by: Virginia NewesNotes
Second Series, Vol. 57, No. 3 (Mar., 2001), pp. 717-721
Published by: Music Library Association
Stable URL: http://www.jstor.org/stable/900841
The conclusion of the reviewer is that this score should not be recommended because of the liberal application of sharps (which are all put inside the score instead of above as is usually done with editorial decisions).
I will keep looking for other opinions of this score.
Interesting, thanks for bringing it to my attention.
Yes; in reading the review this bar was cited in particular as an example of her liberal application of sharps. The reviewer cites the reluctance of editors to alter the cantus firmus except at cadences, as is done by Leech-Wilkinson at the end of the KYRIE I when both the c and g are raised for the last consonance. But to do this for every instance of a imperfect interval (3rd; 6th) moving to the octave or fifth is unusual, especially if it means changing the cantus firmus.