The EmonTX Shield does not have RF installed. The Ethernet Shield is a generic W5100 based on.
I wanted to the the EmonTX Shield to monitor energy use and have its data available for Modbus polling by my SCADA system. These days most Modbus data is sourced over IP.
The three boards work well together without any hardware modification. The EmoxTX sketch simply has inclusions for the ethernet and modbus. The rest is very straight forward. Shield_CT1234_Voltage_Serial_MB_Berawa.cpp :
https://github.com/Balipeace/EmonTX-Shield-Ethernet-Modbus.git