Very interesting operation indeed.
I've seen some of this kind of operation before except it was plastic drinking cups for a fast food chain.
The locomotive bodies appear to be vacuum formed rather than injection molded. The small detail parts the young lady was trimming out were injection molded and are connected to sprews. The logos and details are being automatically silkscreened on to the parts. This ensures the ink-coverage is consistent.
The process is quite labor-intensive, which is why everything has been moved sadly to China where their labor costs are so much lower.