Note that all this information is 20 years old and is badly outdated. Many of the facilities mentioned (eg the Nouchimi Outfitters gas station) no longer exist. https://www.facebook.com/TabascoADV/photos/a.696618650541057...
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The James Bay Road exists essentially as a service road for a bunch of hydroelectric infrastructure that's part of Quebec's James Bay Project. I've never gotten past planning a trip up, but I gather much of the traffic on these roads are transport trucks delivering supplies to these remote locations (beyond what can normally be shipped up there by Hydro Quebec's aviation fleet, which as I understand is mostly wet-leased from Air Inuit and can land on many of the unimproved strips near the major project sites).
Anyway, little outposts like these might've been maintained by either Hydro Quebec on an emergency basis for these transports, or by volunteer (sort-of) trail associations, or by the province itself, or a combination of the three.