While I personally do not
recommend doing pretty much any electrical work live that can be shut down.. I have replaced underground fed panels hot before... one of the power companies here will disconnect for you, but will not reconnect until the city signs off, calls the power company, & then the power company will "try to squeeze you in". In all taking about 3-5 days where the customer has no power, which makes for a not-so-happy customer, with a defrosted refrigerator & spoiled food!
In the service industry, people want their power back on -yesterday- even when a panel goes down due to failure.. I charge an extra $800 to do a hot connect in this area.. or give them the option of waiting for things to matriculate through the city & then the power company...
Hair-raising stuff!, when I do
do a hot connect, I'm wearing long rubber gloves which go to the elbow, a welding face shield, & a heavy wind-breaker jacket, while standing on a thick rubber doormat I keep for this kinda thing... & then smoke about 6 cigarettes once its hooked in!