My 744 TM say that the Main Standby Bus powers the following:
Avionics and warning system status assembly
Flight Control 1L and 2L AC
Left ADC
Left ATC transponder
Left EFIS control
Left EIU
Left FMS-CDU
Left ILS
Left MLS
Left VOR
Primary trailing edge flap control AC
RMI
Right ADF
Standby ignition 1-4
Standby instrument lights
Upper EICAS
So, on the basis that there is no point having primary (i.e.hydraulic) trailing edge flap control AC if you can't run the flaps, I would think they should run with Standby Power only.
If TE asymmetry is detected in these conditions (if it can be), I would expect EICAS caution message FLAPS DRIVE to be displayed and the associated FCU for that group to shut down.
Hope this helps ...
JD
