A branch landing on a power line isn't particularly rare. This video catches something quite interesting, though. Notice how the final explosion of electricity completely extinguishes the flame. Not unheard of but also not something many of us have actually seen.
The example below is yet another branch on a line. While the branch is much smaller, the video is just as impressive. You can clearly see the plasma as it arcs up into the air.
Yes, I live in Oz and all new estates now have underground power (have for 20 years now) but the gut feeling I have is that if the whole city grid was underground that the capacitive load would be horrendous. We often have power outages in summer because when the government privatised the power distribution maintenance and infrastructure planning (forward thinking) died.
I wonder if it's feasible in this day and age to run high voltage DC underground (to offset capacitive losses that would be higher) and then convert to lower voltage AC where it's needed? It would help reduce arc over events due to ice & trees etc. or downed poles due to vehicle accidents. I wonder what the leakage and conversion losses would look like in comparison?