City property they will likely call the city maintenance dept which whether you like it or not may or may not be able to do repairs etc and make that necessary determination. Even the one patrolman and a dispatcher small town PD near me do as much.
The maintenance department is most likely called in the case you mention because they usually have the needed information about the building INCLUDING WHERE THE GAS LINES RUN INSIDE AND OUTSIDE OF THE BUILDING! {that the contractor will need to know if called and hired} If you are an actual contractor then you would know it, understand it, and I would not be wasting my time explaining it to you which makes me think you know not what you say you do. I think you specialize at installing Al Gore Commodes myself. Seem to remember a discussion on this.
The contractor likely would not respond to the emergency as an emergency responder at least not a general plumber. The fire department and gas utility would be first responders along with maintenance dept because the FD Captain would discuss next steps with them before leaving.
Bye Now.
As a California plumbing contractor, I like it when a maintenance man is around that knows the building, or the shopping mall, or the high rise condo building, but it is rarely available.
I don't recall ever needing anyone to show me how gas lines run from the meter, when you have run gas lines yourself for decades, you get a pretty good idea how things run, and I don't recall that help being available, but it is always nice to have someone around that can unlock doors for you and such. I don't know whether some plumbers used to bully you or what, but it sure is amusing to learn how much you dislike the plumbing industry.