Well, I'm out of this game now (thank god, the crazy way things are going) but as I recall the SOP was quite unequivocal, for a bomb warning on the ground:
Park where directed (somewhere remote)
Deplane (note: NOT evacuate) (IIRC without pax hand luggage)
I certainly would not expect an evacuation.
I certainly would not expect to remain sitting on the jet either.
CPB