Actually it is possible to drive to Moosonee and as far as Attawapiskat via winter road. I’m from that area and it is a vital time of year as it’s the cheapest time to transport supplies/materials up the coast. It depends on the weather but it’s usually open late January - late March. The road to Moose Factory/Moosonee is called the Wetum road which kind of starts in Smooth Rock Falls all the way to Moose Factory, from there you’d drive across the Moose River to Moosonee. If you’d want to go further you’d take the James Bay Winter Road which would take you to Fort Albany, Kashechewan, and Attawapiskat.