The treasurer of a city is the president of the city company. This company runs all buildings, that are owned by the city (apart from police station and court house, which are under the CoP's and CJ's rule).
The treasurer is appointed by the mayor and got meet several requirements:
It's the job of the treasurer to keep the city's infrastructure running flawlessly. The most important thing is keeping power plant and water reservoire are at perfect quality and condition at all time, to make sure, that the Basic Facilities (Electric and Plumbing System) stay perfect at all times. If the Basic Facilities drop, the majority of the perfect locales in the city will go incredible for example.