The coolant line is connected to a bypass that circulates heated coolant directly from the block to the critical point in the intake. The coolant heats up fast enough that any ice that may build up would be taken care of pretty quickly. Using my Scangauge II, it takes a couple miles worth of driving for the coolant to heat up the coolant to about 150 degrees. It might take longer in colder climates. A place like Fairbanks, a block heater might be a good idea to shorten the amount of time it takes for the engine to reach full temp. I know it makes a huge difference for me here in PA where the temps don't get any where near as cold. At 4:30-5:00 am on a cold winter day, I want that engine to heat up as fast as it can. I hate early mornings and I hate cold. Anything to make the morning a little bit better, I'll take it.
The icing in the intake acts like an air restriction that can reduce power if it gets too severe. It's a problem in ground vehicles and down right critical in piston driven aircraft. Especially since the carburetor is usually on the bottom of the engine. So heat from the engine can't warm up the carburetor.