There are two main ways by which a contactor may be used to control numerous lighting circuits.
Firstly, a number of lighting circuits may be wired through the same multipole contactor, for example take 8 standard lighting circuits, routing the hot wire of each through one pole of an 8 pole contactor. A single switch may then control all 8 circuits.
For larger installations it would be common to install a dedicated sub panel for the controlled lighting.
As many lighting subcircuits as desired may be run from this panel in the usual way, but the feed into the panel is controlled by a suitable contactor.
Either scheme not only allows numerous lamps to be controlled by one switch but also may save a lot of wire, since only one 2 wire plus EGC need be run to a distant switch. Contactor control may also allow smaller wire to be used for the lighting circuits, a long circuit via a distant switch may need upsized wire, but a shorter circuit from panel to lamp via a contactor might be OK in the code minimum.
As a design note, I consider it very poor practice to control all the lighting in a large office, factory, retail store, etc by a single switch and one or more contactors. Too much risk to life if the contactor coil fails or the cable to the switch is damaged.
I would regard TWO contactors on TWO switchs, each controlling half the lighting to be an absolute minimum, and then only with care taken to avoid any mishap affecting both circuits. Control circuits to the two contactors to be via seperate cables along different routes, to physicly seperated switches. NOT a multicore cable feeding a twin switch.