Zener,
Assuming you are right, and that Xray damage is a myth, why does Kodak recommend that their films aren't put through Xray machines?
Try
http://www.kodak.com/global/en/professional/support/techPubs/f4016/f4016.pdf and look at page 19 onwards, describing their Tmax 3200 speed film:
KODAK PROFESSIONAL T-MAX P3200 Film is very
sensitive to environmental radiation; expose and process it
promptly. Request visual inspection of this film at airport
x-ray inspection stations.
They don't sell it in 120 format as it gets fogged by cosmic rays - they only sell it in 35mm canisters. Sure, this is a very high speed B&W film (actually it's ISO 800 which isn't that high) and is typically pushed. But the silver emulsion isn't anything clever, so if there is an affect on this film it will apply to all films? The advice is from 2007 so not that old.
My belief is that for most films the exposure from cosmic rays/xray machines etc falls below the pre-flashing limit, so in effect you get no change in density. The push processing expected of the 3200 speed film may be why the effect could be noticed?
But still, Guy, you aren't supposed to have exposed film lying about - you are supposed to develop it straight away, collected by motorcycle courier with a coolbox, with a police escort, and rushed to your photolab.
Cesare