"Unstoppable" apparently was loosely based on real events, but the way some of the characters reacted to a dangerous situation was a bit unreal. However, it did remind me of an actual event here in Melbourne - the runaway from Broadmeadows back in 2003. .
CSX8888 set sail after the driver screwed up the power-dynamic braking transition, not allowing enough time for the contactors to setup before he notched up, instead of increasing DB, he increased traction power and didn't realise before he got down to change a set of points. Consequently, the loco powered up and off it went. Because he had a full independent application on, the deadman was suppressed by design. IIRC the 80 Class had a similar setup for controlling dynamic, though it's well over a decade since I drove one of them...
The worst part about Unstoppable to my mind was the throttle moving by itself. That's impossible and everything from that point was based on a lie. Had they had his portable radio fall and knock it, or his coffee cup, even a short in the MU cable or
something it would have been more believable.
Broadmeadows was a bit different, in that the brakes released and the set rolled under gravity, even after Metrol isolated the overhead, it kept right on going.