Well I am able to get it to work just fine with xEnviro. You just have to inject the xEnviro weather into the xPlane weather for it to appear on the IXEG radar. IXEG takes its info from the xplane weather page. xEnviro is a separate engine and does not interact with xplane weather. However, if you set xplane weather to use custom weather and point it to the xEnviro generated METAR.rwx file, it will use this to generate rain and rain echo on the radar. Of course this relies on the METAR info and might differ from what xEnviro shows, i.e. the xEnviro engine might be outputting rain at altitude when the METAR shows no rain, so you won't see it in this case.
Hope this helps.