This is what we here in the northeast call a HOT 3-way. Most common place you will find this type of 3-way set up is at dairy farms with a center pole service, and there is a set of floods on the pole and milk house. The 3-ways are fed at the house and from the barn panels. Russ M has the correct wiring of the 3-ways. The 3-ways MUST be fed from the same phase at house and barn. So when working on this type of set up, you must turn off power at house and the barn.
Shoot first, apologize later.....maybe