Public transportation in Burgandy

I will be traveling witrh my wife to France in late September.  We will spend a couple of days in Paris and then take the train to Auxerre.  From there we have to travel to Baye, on the Naivernais canal, for a week's voyage north to Mailly-la-Ville. 

It seems next to impossible to find transportation information, including costs, for travel within Burgandy.  Specifically, where can I get  bus schedules and prices for Auxerre to Baye, and for           Mailly-la-Ville to Auxerre?  I would prefer to travel by bus, but failing that, how much must I budget  for for a taxi for each trip?

Any advice will be gratefully accepted.

Ariehz