push-pull explanation
The two transistors are configured as emitter followers, which means that they have a very high current amplification.

The BC849's collector is connected directly to 3.3 V, so when Debug is high (at 3.3 V), VCE is forced to about 0.7 V (it cannot saturate). In this case, the collector current is always much higher than the base current:


source: ONSemi BC849 datasheet

In other words, it is not possible for a base current to flow without a collector current.

Furthermore, the base current is very small (the transistor limits it by itself), so it is not even necessary to have a base resistor.

This circuit is commonly used when you need to drive a load with high currents, and you can afford the 0.7 V voltage drop across the transistors. (See, e.g., H-Bridge with emitter followers.)