First understand that not all -400's are fitted with a dedicated transfer pump.
1) those that have the pump fitted, scav the remaining fuel and deposit it into the #2 main fuel tank. The transfer rate is very slow and is effectively negligible. i.e the rate of transfer will not keep up with the requirements of engines running. (well maybe just one eng at idle -trans rate is approx 750kgs/hour) In flight it will come on for these reasons (from the manual)
Two conditions will cause the pump to run for two hours or until the
pump pressure switch senses a low pressure for five minutes:
• In the air with either CWT Override/Jettison Pump Control
Switch turned on and its respective pump is not developing
pressure,
• A 30 second pump On Command when the Reserve Transfer
Valves are opened.
2) later aircraft have a 'hydromechanical' transfer system that will transfer fuel from the CWT to both #2 and #3 tanks. It will operate any time there is pressure in the crossfeed manifold but fuel will only transfer to the tanks when a float valve is uncovered to ensure there is capacity in 2 and 3 to receive the fuel. The transfer rate of this system is even slower than the dedicated pump -i.e very slow and not to be relied upon to keep 2 and 3 topped up to allow feed of the engines.
So Yes, if BOTH your CWT trans pumps quit, technically you can get the fuel out, but it will be at a rate that will be of no use to you during flight.
Clear as mud !
.