I've tried researching the narrow gauge tracks here, but have come up with nothing. 
My guess is that it's likely just a way to get poles moved from the building that makes/prepares them(?) by some sort of Logging Disconnect railcar - similar to ones used on old logging railroads, to an area where they can be put into a pile, then eventually brought to wherever they need to go by truck, or the standard gauge spur right next to the facility. 
The tracks are narrow gauge likely because it allows for sharper curves, but it would of probably been quite cheaper to simply make the tracks standard gauge, as there's an abundance of equipment, railcars, and locomotives in North America made for standard, compared to narrow.