This is just simply an option that a building official may choose if he feels it is warranted.
Building officials generally do not mind helping a business or school open on time to meet promised schedules. One example of this privilege that can be granted by a jurisdiction is opening an educational building to meet deadlines for the beginning of a new school year.
Generally the criteria required is that all life-safety features are installed, tested and fully operating.
The contractor or owner will normally need to put the request in writing to the jurisdiction asking for temporary occupancy. Working in a cooperative spirit with the building department during the course of the construction project will help to make this privilege possible at the end.
Remember, you will need to ask to make it happen.