Having been in the Canadian arctic with an issued FN, I can tell you they work just fine, and there was a good reason why the C1A1 came with wood furniture. The other C1A1-specific features were that you could fold the trigger guard into the pistol grip for those times you needed to wear three gloves over another, and the fold down cocking lever to reduce snags.
In our boredom up there, we did have plenty of time to experiment.
Lube/other info:
Use a really thin oil. Spray-on break-free is what many of us used, some even used WD-40 (I know, you're all cringing now). In the modern world, I'd probably use militec. Both spray break-free and militec will work through the widest temperature ranges, and WD-40 and break-free will displace moisture.
ONLY oil the breech block carrier to upper receiver interface. It's the only part that's under stress anyways.
Re-Zero. I can't stress that enough. A change of 20C to the temp of the FAL will make some things wiggle differently. Your rifle will have a higher variation of temperatures, so the military standard three shot groups will be a lot more wide. As a hunter you'd know that the flier is the cold shot anyways, so that's what you want to get your zero to repeat on. The best is if you can test at your top ambient temperature, and your lowest, and see how much and in what direction your rifle's zero changes so you can compensate. Don't wargame that too much though, it's not as if you're shooting a Parker-Hale or Remington 700. Obviously this won't matter as much if you intend to do shots at less than 100 yards or so.
Try not to bring it all the way to your living quarters at the end of the day - this is where condensation meets lubricant, and they will both work together to surprise you the next morning.
When things go wrong:
1. You probably have oil where you shouldn't. Primary suspects will be on the trigger assembly and the hammer pivot. Oil + moisture + cold + mechanical agitation = butter/margarine/facial cream, and that gets real hard when cold.
2. Oil on the piston, or got blown up through the gas port jamming the regulator or plugging something up.
Speaking of the above, I can't wait to get around to getting my DS Arms congo rifle. Does anyone make chrome lined barrels for these things?