Whether residential or commerical, section 2-308 still applies. For equipment rated less than 1200A, below are the two applicable rules:
(1) A minimum working space of 1M with secure footing shall be provided and maintained about electrical equipment such as switchboards, panelboards, control panels, and motor control centres that are enclosed in metal, except that working space is not required behind such equipment where there are no renewable parts such as fuses or switches on the back and where all connections are accessible from locations other than the back.
(2) The space referred to in Subrule (1) shall be in addition to the space required for the operation of drawout type equipment in either the connected, test, or fully disconnected position and shall be sufficient for the opening of enclosure doors and hinged panels to at least 90 degrees.
Couple itmes to note that may be usful:
-It is permissible to install electrical equipment in a closet or cabinet, provided that the working clearance described in the rules above are met when the door(s) are opened.
-Installing a panelboard in a location where it would be behind a door (ie: someone could open the door into you while you're working on the panel) would be considered poor practice...although there's nothing in the CEC that says you can't do this.