Hmmm... I've just checked the three sound mixes on the Blu (DTS, Dolby 4.1 and Dolby 2.0) and not only is the "Kane's son" line present on all of them, the take used for Dallas' "Morning Mother" sounds exactly the same! I even popped in the 20th anniversary DVD for comparison - the two tracks on that release sound no different in those scenes.

Is the '95 laserdisc possibly the only proper preservation of the 70mm mix? Thanks for the reminder of that, by the way. I've never seen/heard that disc but I was aware of its existence. I wonder if that track has ever been extracted (not sure of the ins and outs of AC-3 on laser).

And I'm aware that these posts have been wildly off-topic, so perhaps we should discuss this elsewhere! It's just that I saw a 70mm screening about 15 years ago, and its raw and vital quality made quite an impression on me - none of the Blu audio tracks have quite the same effect.