That's too bad. A good rule of thumb is to always bury the dynos, recover and then make an Automatic set without bailing...while in the yard and light power...as you make your way to tie on to your train or get to the main line. Even at the low speed of 10 mph or less, a good hog will know by the feel of it if everything's cut in. But, a lot of places already have the power tied on and you just have to take it in good faith that everything's working as intended. Aside from that, it's possible that everything was working fine when they left. It's common for things to fail enroute, and you don't always get a ringing bell from another unit.

On the Mojave Sub on the UP, (and on the Cajon Sub on the BNSF), a running air brake test is required before cresting the summit northbound before Tehachapi, and before dropping down into Cameron southbound. While this doesn't address the dynamic brake question to a great degree, if any, the notion that 'We're about to go downhill' is foremost in mind. Without looking it up, I'm confident that even if it was light power, the rule would be the same.

Beaumont hill is deceptive. You can drive it in your car along San Timoteo Canyon road and not really notice that you're climbing a significant grade. I've never been on the territory as a crewmember, but growing up in the area I learned that the rail grade is significant; lots of evidence of that. I wonder of the Yuma Sub has trainhandling/train make up rules addressing the grade?