2-300 covers maintenance in a generic way but often testing is covered by building code say for a life safety generator needs monthly tests as might the unit equipment supplying exit or emergency lights.
Circuit breaker manufacturers recommend yearly exercising of breakers (turn them off and on a couple of times as this serves to lubricate the mechanisms but we all know that no one does this.
CSA is currently publishing Z 463 which should eventually become a Standard for maintenance but now it is only a guide.
