Is there a requirement for Electrical Design Engineers to show all his/her design computation/analysis used on electrical plan?
Normally there are voluntary guidelines recommended for Multi-Unit-Residential-Buildings (MURBs).  We do not know your circumstances.  I extracted the following from recent guidelines written for Toronto, Canada.


  During sustained area-wide power outages, emergency power is not designed to keep residents in their buildings with any degree of comfort, even if there is no particular problem with the building. However, backup power is provided to meet non-life safety requirements that are considered essential for occupant
  well-being (e.g. water supply, heating, elevators), such that occupants can remain in their building safely and with a degree of comfort for at least 72 hours.