The 'CITY' wants it done live - a COFFE SHOP...This sounds very political to me.
Most electricians are not properly trained to do this work. OSHA does say it can be live if removing power creates a hazard...Give me a break, I mean give those guys doing the work a break
I hope this contractor has a written procedure and documentation of the proper training or he may be in big do-do.
I agree with a generator temporarily feeding the coffee shop if they want to keep it open.
I SEE ABSOLUTELY NO GOOD REASON HERE TO KEEP THE POWER ON - SHOW ME ONE GOOD REASON!!!