The best-known collector of Franco-Manitoban music is probably Marcien Ferland, who published Chansons à répondre du Manitoba in 1979. Here's his bio:

http://www.thecanadianencyclopedia.com/index.cfm?PgNm=TCE&Params=U1ARTU0001191

You can order the book here (C$24.95): http://www.livres-disques.ca/recf/products/product_detail.cfm?id=5212

It's an unusual collection and the music is quite different from the eastern Franco repertoire of Quebec and the French Maritimes, both in terms of text and tune shapes.

Since 1988, I have presented a musical living history roleplay of a Métis woman in the NorthWest Company fur trade. I also became bilingual in French in the process, which helps when doing Web research ;-). I've had the opportunity to play and sing with some wonderful Franco and Métis musicians, most notably at Festival du Voyageur at Fort Gibraltar, St. Boniface, MB where I bought the Ferland book. If you haven't been to Winnipeg, Fort Gibraltar is a must-see. (And yes, I spent a week there in February in 18thc clothing...) http://www.festivalvoyageur.mb.ca/portal/index_eng.htm

More info (including MP3s and research articles) here: http://homepage.mac.com/lynnoel/crosscurrents/solo_programs/lisettes_journey/

I'd be glad to correspond offlist with anyone looking more deeply into French-Canadian and Métis music. I'd also very much like the sheet music for La Métisse when it becomes available!