I live in Fairbanks, Alaska where the side roads remain iced up the entire winter My children rode a bus to school for the twelve years they attended school. The buses were, and still are, equipped with the automatic chains to navigate the hilly residential areas.
The chains are self cleaning from impact and only get extended while the bus is in motion. Replacing lengths of worn chain is inexpensive and simple. The expense is in the original installation and are not cost effective unless used often.
Regular chains must be put on, labor intensive, and then when the hill has been cleared the bus has to stop again to remove the chains, labor intensive. Time is money.