Yes and no,,,,,, allow me, the speed brakes as well as the gear doors are open during taxing.
If the aircraft arrives at the chocks and they are NOT opened and the aircraft is shut down before it is noticed (it happened, not that often but it happened), ground crews would have two choices to open the speed brakes and gear doors:
1) Hook up the air cart and motor the engines so they could be opened up this would require a engine run certified ground crew member to do this since not all ground crews were certified for this.
2) Hook up a hydraulic test stand and a power cart, pressurize the systems and energize the aircraft, then open the speed brakes/doors.
The "unofficial" was to open the gear doors was to pull the alternate gear release handle of the left side of the front cockpit or if your arms and hands were small pry open the gear door locks with a screwdriver.
It has been 20+ years since I worked on them so some procedures might have changed.