The AZL Bethgons were indeed designed and tooled by Bowser. The first run, NS, Conrail and CSX were produced by them. Since then, AZL has switched their production to their new manufacturer in China. The second run of UP, BNSF and CHTT were produced by them. There are some differences. For instance, the loads have been enhanced in the 2nd run. Most future Bethgon runs will be coming from China, though we may see one or two Bowser releases.
As for the High Cubes, these were all China. All future rolling stock from AZL will be coming from the new supplier. As for the TTX High-cubes... well it is an accurate paint scheme.. but not quite for the body style released. They bodies are very close. In following the other Train board Thread, and knowing AZL's research, I can see how this happened. The biggest issue is that AZL went with a body style used for auto parts which has more ribs than the TTX High Cubes that were used for lumber products. Since the ribbing is slightly different, it throws off the printing. In would have been impractical for AZL to produce two different cars for the ribbing issue. The good news is runs like the NS cars will be spot on since they use the more robust high cubes.
Interesting enough, freight cars can be extremely difficult to research. They are not photographed as much as locomotives and finding detailed photos or reporting marks and such is nearly impossible. All manufacturers have to take some liberties and best guesses are common between all the manufacturers.
Rob
