well, each company has to provide their schedules to the online travel planners. Not many railways offer travel planners for the whole of Europe, DB and ÖBB do so and use HAFAS software - and as said before this programme can only offer those schedules for which data has been provided.
Trenord obviously has decided not to send data (yet), so you have to look for schedules on their website.
Regarding InterRail/EuRail on Trenord, there are no official news at the moment but we were told that TreNord should be officially accepting IR/ER soon. Meanwhile staff should accept passes anyway, which we got confirmed by several travellers in the recent past.