What's the voltage transfer characteristic of this power driver circuit?
If you assume that the opamp is a rail-to-rail device you can then say from inspection:


The configuration has unity gain.
At zero load current the output limits at approximately +/- 4.3V (one V(be) drop from each supply).
The configuration will clip at approximately +/-70mA and the output voltage will reduce linearly (the 10 Ohm resistor) above that current. This is calculated from the current flowing through the 10 Ohms resistor that would cause the transistor to be fully saturated (Collector just a few mV above Emitter). It is only an approximation of course without detailed transistor specs.
The diodes serve no apparent purpose at all, positioned as shown on an output. To cause conduction you'd have to raise the output terminal above/below the supply voltages. If the output voltage is within the supply rails then the diodes can never conduct. They were possibly added to the circuit simply as obfuscation. 


With device characteristics you could further calculate the limits.