Not trying to sound like a wise... ,I dont know the river,but Ive never heard of trouble launching a canoe.I take it its mostly private prop? a quick google search found this http://www.paddling.net/places/MA/[/url]
thought I read river,my bad....now I'm a dumb.. 
I think you'll find what your looking for off Edwards Rd. http://massbassfishin.blogspot.com/2010/07/neponset-reservoir-foxboro-ma.html