No... The outside temp probe on the mirror has nothing to do with emissions...
IAT is an acronym for Intake Air Temperature. The IAT sensor measures the air temperature that is going into your intake manifold. The colder the air, the more dense it is, and the more fuel you need to keep your engine happy. Coool ....literally. Almost all IAT's are simple two wire devices that measure resistance. As the air temperature changes, the resistance in the sensor changes and the ECU knows to change the A/F ratio based on this. Combine this data with that of the MAP sensor and your computer can now give a pretty accurate guess of the volume of air moving through your engine. This is great news, but it's all based on calculations, instead of real solid numbers. This is where speed density is tossed aside and big Mr. MAF enters the party
Usually the IAT is tied in with the MAP on the promaster.
If the outside air temp on the mirror controlled the emissions computer you'd be having a lot more problems ....