Upvote:4
As you can see in the agendas, you are probably out of luck. Additionally, I think that most of the sittings listed named like "X-Ausschuss" are only partially public and you may need journalist accreditation to attend (especially the BVT-Untersuchungsausschuss).
More information can be found on the English website but I guess you have already seen that. I would suggest you ask the visitor service directly using the phone number provided on that site.
If you are still in Vienna, check if you can go visit the emergency session scheduled for tomorrow Monday, 19.05.[several parties wanted a session immediately as of Saturday] this week[later date was pushed back] after EU elections - it is sure to be dramatic and lively as the resignation of the vice chancellor and the associated scandal are to be dicussed.