The OneWire protocol used by the Dallas chip is bidirectional. So it can't work with the opto-isolated inputs.
If you anyway need 3V3 and GND from P1, why not keep the dallas "microlan" on D2 ? If you want, you can put many sensors on the same line as they have unique IDs.
Note that analog Arduino pins can be used as digital, so you can use the A1 and A0 as OneWire as well.