I hear you with that theory. However, pasturization temps are significantly lower than that of the coolant/water in your radiator. Radiators get up in the 200's under way more pressure than what would be in a bottle.
I assume the same laws of physics apply to most things, but the variables are different here. Radiators are under the range of 10 to 20 lbs of pressure (from memory) depending on the model of car, and thats to keep it from boiling at waters normal boiling temp. Home brew would be lucky to get half of that pressure and my mind makes me think that the fact its CO2 providing the pressure, as opposed to heat and steam, that it would work a little differently.
And again like I said the temps required for pasturization are far less than that in a radiator. Good point though.
Thats just my thoughts on the topic anyway, I could well be wrong, wouldn't be the first time.