The normal parking...north face... for the path up to the Allt a Mhuilinn access to the Ben area is at the turn off at Torlundy for what I think you are asking about is accessed from close to the Skiing area base.
The only time that I have been up on the tracks through the forestry plantations was in a emergency services vehicle. The gate needs a key to give access here. Probably most road vehicles unless having an off-road capability would struggle I guess to get up here with snow on the ground.