Question RE: pressurization and aircraft evac

[Rugerdog]

I work with ground crew at KDFW. Recently, an incident at Ft. Lauderdale occurred in which a deranged pax forced his way off of Continental flight as it was taxiing to the active. Reportedly, the pilots depressurized the cabin in order for the F/As to be able to open a door and allow the man to leave the plane.

My understanding of newer commercial airliners is that the pneumatic system, when set to AUTO, doesn't begin to pressurize the aircraft until approximately 60+ knots of groundspeed has been reached on takeoff roll. Is it standard ops to pressurize older aircraft at the gate or during taxi?

Also, in the event of an aborted takeoff with a pressurized cabin, does the outflow valve automatically revert to a fully open position or does the aircrew have to manually open the valve to depressurize the aircraft in order to facilitate emergency evac should it be required?

Thanks.