This will depend. I would often suggest you don't rely on this being an option.
Pipe was mostly used for lighting so it's unlikely that you will be able to do this with your socket outlets.
Properties that were wired in pipes were mostly flats from the 60's and 70's. Whilst you could rewire a flat that was originally wired in pipe, its common for the pipes to corrode which would make pulling new wires in difficult.
Some wiring will have been installed by using capping: a PVC or steel cover that goes over wires. Again, don't rely on this, as there are likely far more wiring systems without this feature than there are with it.
Lastly, some wiring systems may have been installed with plasterboard dot and dabbed over them. In some cases, you can run new cabling down these small voids, but again, its mixed results and shouldn't be relied upon.
