I'm not sure why they had three P42's on in the first place, unless one was being moved for some reason.
However and I admit it's hard to tell for sure, but frankly it sounds to me like the first two units (141 & 46) aren't running. I only hear engine noise from the trailing P42, #136, which is no doubt supplying HEP. Even if Amtrak had a place to turn the locos after 141 failed, I'm not sure that one P42 has enough power to pull the normal consist, supply HEP, and move the weight of three engines over the road. Hence the reason for getting help from NS.
So both lead units failed... that would make more sense. And no, I wouldn't think that a third P42 could pull the dead weight and supply HEP.
The question in my mind is: why did both units fail? And how lucky were they to have a third on the consist...
Well again, I'm not positive that both the lead units failed. I just doesn't sound like they are running as they pass the cameraman. And it is possible that the second unit was dead upon departure. It may have been getting hauled dead for some reason. Again, I don't know, maybe it was running when it left NOL. But it is odd to put three on the train to begin with, so I suspect that it may well have left dead.
At one time NOL used to have a loco shop, technically it's still there, but I'm pretty sure that it was closed a few years ago. So any b/o'd unit would have to be shipped back out.