Yes, I intentionally set the ID to 0 to test for interference.  The RFX-250 is plugged into the RF in.  I have tried the 3.5mm connector and the screw down connectors.  I have also tried another RFX-250 as well.  I have moved the id selector to the other positions.  All the models are the "i" version.  No matter what I get the same lights.  Both the power and RX lights on the RFX-250 and only the power light on the MRF-350.  No flashing just solid lit.  I've tried it in two locations and I'm reasonably sure it is not interference.