I caught it at Celilo, OR crossing the Columbia river Saturday afternoon.
This will most likely head north to Interbay (Seattle) as over the past week three other cabooses (1-ATSF, 2-BN) have moved north on the end of trains.
No one has commented as to what maybe occurring with these hacks, but one could wish for a Heritage Caboose fleet since they have already painted one into GN.