Even though I don't know much about PhoneNet, I have to agree with
@LaPorta, because logically, why would PhoneNet have been designed to be compatible with ordinary telephone wiring, yet require a special kind of crossover cable in order to work?
I'd suppose it could've been intentionally designed to use either, maybe with a preference for crossover to ensure optimal throughput, with a fallback mode to ensure maximum compatibility with standard phone wiring, but I'm only speculating here.
c