The OneWire bus software will enumerate the devices in numerical order. However, the numerical order isn't quite what you'd expect. For example when I run a sketch to identify two DS18B20s it finds them in this order:
ROM = 28 D4 C9 0 4 0 0 49
ROM = 28 1E BD 0 4 0 0 6B
Looks like it has got them reversed but when it enumerates them, it checks each byte of the address low order bit first
The two addresses obviously differ in the second byte. Writing the bits out and then reversing them:
When the address is rewritten with the bits in the order that the enumeration protocol does it, you can see that what we write as 'd4' is seen as '2B' by the enumeration software.
So, the answer is that the devices are indexed in numerical order of address with the low order bits of each address byte checked first.