There is the Northair Gold Mine - attached a map from Gaia. A local quad touring company takes people up there so have done some improvements though it's Crown Land so no ownership issues. I see they've made a lot of quad tracks but have never followed them due to lack of time - might be worth checking out. I also attempted to get into Jane Lakes from the North - probably doable, but I hit a steep rocky section and riding alone so decided to turn around. I see by BRMB ATV map overlay that the access from the East side suggested its a workable route. If you're dual sporting, it might be interesting to link up the Mine & Jane Lakes, but might not be worth loading and unloading - Cat Lake & Lava Flow are only a short drive South and much more riding options for dirt bikes.