Piper 19
I understood that the original question related to a flight condition. You are correct in stating that the left forward boost pump will run anytime AC power is on the aircraft, irrespective of the the switch position, but how do you start the APu when no AC power is available. Dc pump kicks in as the left feed manifold is not pressurised until APU is a 95% and on line or ground power is applied.The AC and DC pump messages will be unavailable until AC is on the aircraft and EICAS is powered. In respect to centre overide pumps, you are correct when you say that they will run when the P28 panel is open (assuming that the pumps are switched on) or the engines have reached 50% n3, this signal coming from the speed cards.
Apologies if I have confused you.