Water pipes which have been exposed to extreme cold temperatures resulting in freeze plugs have been known to fail “burst”. Is it the cryogenic effect on the piping material that is actually responsible for such a pipe failure?

NO! When water freezes within piping it develops an internal freeze plug which grows outward in both directions of the pipe ID. If this outward freeze plug growth is allowed to form against a short dead headed section of water piping, it will create an enormous buildup of water pressure, which can eventually cause the strongest of pipes to burst.