Are there any airliner crashes that can be definitively attributed to Mach tuck?
I've never heard of one, but note that the pitch down effect of Mach tuck starts  below Mcrit, and below Mmo for that matter, and airliner trim systems have a "Mach Trim" function to drive the stab to counteract it.  

Fortunately, in the speed range of a commercial airliner, the amount of tuck is modest and it's not really a controlability issue, just an increase in trim speed.  Flying manually without Mach Trim, it would just require a manual trim input to keep the nose from dropping.  If the autopilot was on, it would take care of the trim change on its own.

So I would say that an airliner would never encounter a mach tuck condition that could cause loss of control unless it was way above Mmo in the first place, which means it was already out of control for some other reason.