[Izzy Dunne]

the motive force for the application of the brakes comes from an air reservoir aboard each individual rail-car, not from a spring.

Are the cars interconnected, brake-wise?

I would think so.

Can a leak in one place drain the reservoirs of ALL cars?

I don't know.

Seems like the engine should CHARGE all reservoirs, but not be able to DISCHARGE them.

But I'm no train guy (in case that's not obvious).

[thackney]

Are the cars interconnected, brake-wise?

The main air supply, that pressures up the reserve tank, as well as holds the brakes open, is connected. Loss of this pressure supply line, closes the brakes, depending on each individual car to hold its own brakes for a time sufficient to apply the hand brakes.

Can a leak in one place drain the reservoirs of ALL cars?

They don't need to all be drained, just enough of them to partially relieve enough pressure. Some were still holding; there was reports of screaming wheels and glowing red brakes.