Is telephone and LAN wiring symmetrical?
You cannot swap wires in the pairs for either, but for different reasons. 

In telephony, the AC voice signal is overlayed on a DC supply, which is used to power telephones. Research starting point would be hybrid. If you filtered out the DC part, and only transmit the AC part, you could actually swap the wires.

In 10/100 Mbit/s LAN you cannot swap the wires, because the signal on the wires is differential, the signal of the second wire gets subtracted from the signal on the first wire. If you switch the wire, you reverse the polarity of the signal, effectively munging the bits. Start out here: physical layer