Downloaded the Canadian official document. ALso read article in OCtober 1999 Business and COmmercial Aviation (a McGraw-Hill publication.) ALso have photocopy of Jeppesen page. All specifically say that altimeters do not compensate for the effect of non-ISA temp on pressure lapse rate above the reporting QNH's elevation.
The terrain clearance you get on a published altitude presupposes a delta-pressure (pressure difference) between QNH reporting point and you flight altitude. That delta pressure varies with temperature. The ADCs, DADCs, and non-electric altimeters will not, cannot, compensate for a non-standard pressure lapse rate, which is the prinicipal threat resulting from the below ISA temp.
If you ask a mechanic, technician, or engineer, you may get a misleading answer. They don't design or fly the approaches; they don't read the charts.
It's the people who design the instrument approaches (FAA or CAA) or who fly them, who will be operationally familiar with this issue.
It is rarely a safety threat because most approaches are precision, and because intercept altitudes are rarely 4,000 feet above MDA. Also remember that when it is that cold, it is rarely poor visibility, so many approaches are done on a visual basis, at visual altitudes.
Most VOR approaches run about 1,500 feet above airfield for the intermediate segment, and about 500 above for the final segment, so the distortions are small.
Now, think about in a night approach on a moonlesss night. YOu're probably flying the instrument approach, yet you're possibly also less-than vigilant on the instruments. You might be a little shocked to see how low you are, AGL, at the published segment altitudes. You'll dismiss it as some sort of optical illusion. What we are telling you is: you actually are lower, reference the terrain. You are at the same pressure level; but due to the non-standard pressure lapse rate, the delta pressure gives you a smaller terrain clearance.
It's quite all right being dubious, but you may be going a bit too far here. Sorry to be a bit provocative, but may I ask when was the last time you turned out to be right when thousands of Canadian airline pilots believed otherwise.