Not really (this is besides the point, but if you're curious...) The magnets actually increase in temperature due to something called Eddy currents, it has nothing to do with contact or an air gap, and they heat up from the inside, outward. As long as your motor is running and producing the alternating fields which ultimately drive your bike, your magnets are going to heat up internally.
The more your magnets heat up, the less magnetic field they produce, and the less power your motor can produce. The whole idea is to keep your magnets either as cold as possible. Now your permanent magnet most definitely has extra additives that make it perform better at higher temperatures, but there's no way of me knowing exactly what that is. Needless to say, a pure Nd2Fe14B magnet has a magnetization curve that looks like this. I took that measurement myself right now with a pure magnet, and it's very accurate. As you increase temperature, the magnetization decreases (quickly!) as you approach the Curie temperature in the neighborhood of 600 K / 300o C. Now, 120o C is about 395 K, so take a look at where that is on the graph. It's at a magnetization of 110 emu/g. If you increase that to 400 K, you'll have a magnetization of 109 emu/g. This is less than a 1% drop in magnetic field. Now, this doesn't directly translate into a 1% drop in performance (your performance drop will be a little more than 1%), but it's close enough to get an idea of how the performance of your motor is effected by a 5o C increase in temperature.
Now I don't understand motors that well. Automatic Transmission Fluid gets in direct contact with the magnets in a hub motor? I wonder how that works, I'm not getting much through Google. Anyway, general intuition of mine says that even in electric cars you want adequate ventilation to your magnet so it can act as a heat sink and cool down your magnet. If sealing the motor and filling it with ATF brings the liquid into direct contact with the magnet, there will be much better heat transfer, so your magnet will cool down much better as long as the ATF is cold, and your magnet would heat up much faster if the ATF were hot. Based on what you say, it sounds like this method of introducing ATF to the magnet is suppose to work by cooling the magnets down more efficiently. If that's the case, then your bike will see slightly better performance.
As for the 80o C, that sounds like a relatively arbitrary temperature. It won't be a permanent degradation of performance at that temperature. Once your bike cools down, your magnet's performance will go back up nearly all the way. I can't quantify it without some technical data on your magnet.
