Interesting points ... but note that several states and commuter agencies have bought F40-class power (F59/PHI, MP36/40, and a few off-brands) in the intervening years. NJT even got some dual-power (diesel & wire). So passenger power isn't unavailable. It's just that Amtrak hasn't bought much of it and true long-distance road power like the P40/42 series isn't in the catalogs.

Does that just reflect the realities of Congress not liking long-distance trains (regionals can be dumped on the states to support, after all)? The new cars loosely based on Cal Cars are for regionals, too, right? Not Superliner replacements. I suspect you won't see P40/42 replacements until you see Superliner replacements, which you won't see unless long-distance trains make a comeback with Congress (don't hold your breath), or unless EPA lowers the boom on the olde ones for emission reasons forcing upgrades or replacement.