Wow. That story is... Frightening.
I always learned (Yank here,) that dialing 911 and then not saying anything would send police your way, lights-and-sirens style. But then, that was twenty-five years ago, when I was just a wee nipper. (Gods help me, I'm OLD! How did that happen?!)
Having said that, I wonder if it's still the case. I've caught my phone trying to call 911 once or twice, usually when I was trying to do something entirely different. I think I always managed to catch it before the call actually connected. Thankfully, the one I have now doesn't butt-dial (also, I never make use of back pockets.)
It kind of does seem like there should be a way to surreptitiously send a signal to the cops that says "I'm in trouble, I CANNOT SPEAK, and I fear for my life, please come to my rescue sirens screaming." Obviously, misuing this feature would be... Well, bad. But on the other hand, having people who get killed while an operator cuts them off thinking that they butt-dialed is worse.
On the other hand, treating every mistaken connection as a full-blown emergency is, evidently, a logistical impossibility. In an ideal world, it wouldn't be, and, just like straight out of the evil overlord list, any suspicious activity or loss of communication would be treated as a full-scale crisis, but you'd need to increase the number of police by an order of magnitude at least.