The Private persons railway might mean the LR, "Lahnuksen rautatie". "Pitäjänmäen rautatie" was one of three russian military field railways near Helsinki. The amount of timber felled was enormous, but mainly it went to all sites of the coastal military installations of the "Peter the Great Naval Fortress" of WW I. See book: "Fortress Railways of the Baltic Shores" by Mehis Helme (Plateway Press 1994). Some information is in bits and pieces also on this website, for example the typical russian field railway locomotive:
http://vaunut.org/kuva/97319?t=outokumpu . Neither of these railways were in Nuuksio, but in that direction.