For anyone interested in trying:
The diagram for the switch is on page D-62 of
http://www.gmupfitter.com/publicat/2...ST_Elec_D3.pdf
Three of the buttons just change the output resistence of prong 1 (maint, menu, set), prong 2 is ground, and the info button prong 3 just grounds to prong 5 as a momentary switch, the LED (prong 4) grounds to prong 5. You'd either have to make an external module to translate the resistance change for the BCM interface. Or, wire the circuit board diferently to actually make the momentary switches work and the LEDs light.