Fire codes and occupancy limits are set by how many people can evacuate the building in a set amount of time. I worked at a place in an antique building and they had to limit how many classrooms were allowed in the building because they had to stay under these limits. Also, yearly, there were fire drills where they'd verify they could get everyone out.

So in tesla's case, they'd just fire all the people who leave their desks in a fire?

Elon will plead to the fire marshal to arrest only him, and force his workers to come in anyways

As if Musk would fall on his own sword let alone anyone else's. To much wasted time to be able to poke fun of Bezos or make some other bone headed tweet.