I've installed MyPIG 1.0 and it do support XMLTV . I didn't get it to work properly though, perhaps the XMLTV standard has changed since 2003 when this software was made. My XMLTV settings are correct since I can use them with GbPVR and MediaPortal.
Even if it would work, reading from it's homepage it doesn't allow scheduling and recording in MC, only browsing, filtering and searching in the TV-guide, so I guess it's not quite what I was looking for.
It's seems like this product is "dead". There seems to be no way to contact the authors and get support. My guess is that it is not possible to "remontely control" J Rivers Media Scheduler and that's why this product was never a success. So - I stil need an answer to the question if it is at all possible to automate recordings in Media Scheduler with the dev.interface?
/Robert