Pin usage for the different Arduino version:
LocoNet interface use for communication Timer1 and in Arduino Mega the Timer5

TxPin set while initialize the interface:

  LocoNet.init(TxPin);


RxPin is on ICP1 and on the Arduino Mega at ICP5

  Arduino Uno (ATmega168, ATmega328, etc.) PB0, Digital Pin 8
  Arduino Leonardo (ATmega32U4) PD4, Digital Pin 4	
  Arduino Mega (ATmega1280, ATmega2560) PL1, Digital Pin 48
  Sanguino (ATmega1284p, ATmega644p) PD6, Digital Pin 14
