I'll guess...... and I do mean GUESS.
1. It sits on a shay chassis. There is no apparent stack, so must assume it's no longer steam powered. Gas or Diesel.
2. The rig on the side is most probably a form of "jill poke" or log unloader. I would guess that a log train would pull up at an unloading facility, and this unloader would start at one end and one car at a time would push the logs off, until the train was unloaded. The train could then return to the forrest for more logs.
3. It appears to be an "in-house" manufacture/modification, and may even still have the boiler in place as a "counterweight" for pushing logs.
Pete