timing chain failure diaster depends on the type of engine.
The main diaster is that a piston slaps into a valve and bends
the valve....

i have a ford truck that has a timing belt and it brakes ever 70k miles...
I just pull over and put a new one on.... the reason there is no damage is that there is clearance room at the top of the piston so its not possible to bend the valve... so no big deal...

i broke a timing chain on a dodge intrepid and it ruined the engine..
bent the valves...it was a 2002 and i did this in 2004...bad deal..

I have 3 mercedes and i have replaced a chain but yet to see one brake..
but it would depend on how close the pistons at tdc come to the valves...