The issue here is related to the fact that most of we canuks see outdoor locations for OCD as rust prone. OC devices are also not temperature compensated. If it is hot the breakers trip early if the panel is in a high ambient. (think Death Valley) but if it is below 0C or 32 F the trip time goes up and can increase OL trips by a lot of time.
For locations where outdoor services are accepted like saw services or traffic controlers there is no building to put the panel inside. A pedistal service for a motor home and such are exceptions. The CEC has adopted a rule that will permit an outdoor main but the branch circuits and even another main inside the building may be required to deal with overload. This allow the protected conductors to run inside the building where a panel migh have a better location than an exterior wall.
