That depends on what part of the manufacturing stage you're talking about. Will the MBP in TX have its printed circuit boards made there? Or will this just be a final-assembly plant, where they ship in the completed components and have some laborers screw them together so that they can claim "assembled in USA!!!"?
The final assembly is likely mostly by hand, maybe using some fixtures to speed things up. PC board assembly, however, is usually automated except perhaps for larger connectors which may be hand-placed before reflow soldering. Those machines, however, cost an absolute fortune (the ones capable of the very high volume needed for consumer electronics), and are usually made in Japan or Germany, and then shipped to China or Taiwan where they're used by contract manufacturers. I would honestly be surprised if Apple actually made the MBP PCBs themselves instead of just outsourcing it to a CM like FlexTronics.
I was surprised to see how much of the iPhone assembly was done by hand. There are videos out there showing the assembly line and it's basically humans doing each step.
