They are two seperate items, and given the circuit schematic for the Shift Interlock System, it doesn't appear as if the Transmission Mode Selector Switch provides any type of input to the Shift Interlock Controller(what it seems you are referring to as the Neutral Safety Switch).
The only way it seems that the two interact is that the transmission control lever can't be moved until the proper conditions are met for the Shift Interlock Controller, that being mainly that the brake pedal is depressed if the engine is already running, or the starter switch is in the START position and the transmission control lever is in the "P" position.