Looking at its location and construction, could it have been planned as a car shop? When was the "garage" built? If it was built by the railroad or around the time that the railroad arrived there may have been a plan to use it for railroad purposes. If it was never used by the railroad was it because rolling stock maint. was done elsewhere. Did it ever have track feeding into any of the doors? If owned by the railroad but not used, the building would have become surplus and sold to a private owner.
All just theory, but I've thought it possible ever since I saw where the building was located.