The EZIOxx Inputs send Insteon Group messages or Insteon Broadcast messages when state changes occur. They do not send X10 messages.
The output relays can be controlled with Insteon or X10 messages. The EZIO2X4 Quick Start Guide describes the Set button sequence to establish the X10 House code and enable X10 control of the relays. Unit 1 controls relay 1 and Unit 2 controls relay 2.