Vertical integration (keeping processes within one manufacturing location) is a great idea, protecting proprietary technologies of product and process, controlling production schedules/quantities, minimizing work-in-process shipping costs, etc., etc., etc..
However, extruding aluminum...ITC, toy train car bodies...is not something Lionel would've ever considered for in-house processing, IMHO. Extrusion of aluminum, the basic process, was neither invented by Lionel, nor did the basic car body contour have unique qualities for which the material and die construction were to be protected.
Moreover, if you read through this link re the process...
AL extrusion link
...there is one line that rings the loudest for me...
"Typical extrusion presses cost more than $100,000, whereas dies can cost up to $2000."
...and that's JUST the press itself, one of them, without the handling/heating/prep equipment, specialized labor/costs, etc.. And, if your market/production/sales projections in a given year were dependent on successful production of items using this process, chances are you'd have some duplicity built in....a.k.a., a second >$100K press, et alia...in case the first set encountered problems. That's easier for a specialty manufacturing shop, one that has multiple presses, depth of labor skills, serving multiple customers with similar product needs, etc., to handle than Lionel....for whom this process would've been uniquely tied to one product line...passenger cars.
All of that process expense has to be absorbed in the cost of the product, ultimately finding its way to the selling price to the consumer. Duh? Oh!?
I'm sure Williams (USA-production era) didn't vertically integrate AL extrusion, either. Nor K-Line. Nor MTH. Nor any other gauge mfr. of toy trains.
And, I'd really be surprised if Sanda Kan did/does. The $$$ and technology-process-labor skill 'fit' really isn't unique to U.S. production. It's the universal way you look at making money, making toy trains.
In my 31.5-years of engineering/management work with a large automotive corporation I visited and became reasonably acquainted with manufacturers specializing in metal extrusion process. While hot or cold extrusion (not sure which Lionel's part would've used) of aluminum was not the process/parts I was involved with, the suppliers' plants were truly 'scary' places to be in. When you're dealing with thousands of tons of pressure pushing hot or cold metal into and through dies, and rapidly handling/processing the resulting extrudate sometimes flying out of the press, you're definitely not squeezing oranges at a juice bar or putting toothpaste on your toothbrush!!
FWIW, always...
And just one man's opinion, of course.
KD