The DC bus is likely at a lower voltage than typical AC circuits, therefore less able to cause electrocution.
It's not the voltage that kills, it's the current. As little as 100mA is fatal if it crosses the heart. And if you want to work with lower voltage for the same job that means the current must be higher.
The higher current goes to the equipment the powerlines are connected to. But that current will not affect YOU in any way. However, if you happen to touch a low voltage line, the current through your body will be lower (Ohm's law) than when you touch a high voltage line. Hence, low voltage is safer.
Try taking the poles of a car battery (12V) in your hands and prodding your electrical outlet (110/230V) with two metal rods to feel the difference. Don't do it the other way round, chances are you won't be able to do the second experiment.
(And where is comes to current: your car battery is able to deliver >100A, while your outlet will be fused for about 16A (in Europe, 230V)).