Had a close call this week and learned that GE Power Break circuit breakers with electric charging motors can still be closed, even if locked out, unless you disable the control power by pulling the control fuses above the trip unit.
Many styles and options exist for these breakers. I'm specifically talking about the old style Power Break circuit breakers with the button you have to push in on the manual charging handle when charging (see photo below).
There's a slot on the button for your lockout, but this only prevents the breaker from being charged manually. The "ON" push button will still close the breaker if it's charged electrically.
Another tech and I had to replace the main breaker of a 480 volt MCC, which was fed by one of these style breakers. We de-energized the circuit and the circuit breaker re-charged itself. That's when we learned it had a motor. We almost didn't hear the breaker charge at first because the CRAC units were running loudly inside the switchgear room.
We put our lock in the aforementioned slot, yet with a simple push of the "ON" button, the breaker closed, re-energizing the circuit. The exact reason why you always try to close a circuit breaker after locking it out.
It became obvious that putting a lock through this slot only prevents someone from charging the circuit breaker manually, no special action is needed to trip or close the breaker once it's charged. Since this particular breaker had an electric charging motor, the lockout was bypassed.
In this case, the solution was to remove the switchboard cover (energized) to access the fuses located above the trip unit (which couldn't be seen otherwise), after pulling those fuses, we were able to trip the breaker without it re-charging. Leaving the lock on prevented a manual charge, somewhat locking out the breaker.
I say somewhat because if somebody really wanted to, they could just rob fuses from another circuit in the switchgear to recharge and close the breaker.
When it was time to re-energize the circuit, the breaker was first charged manually and then the fuses were put back in to prevent electric charge while installing the fuses.
Be extremely careful when locking out, and working on circuits fed by this style of breaker.