I read on the forum that SparSchiene tickets are non-refundable. Is that correct. Do the same regulations apply to MAV and www.cd.cz tickets as well?
Well, it is not just Sparschiene tickets, but usually cheapest discounted tickets (many names in different countries) are non-refundable/non-exchangeable, basically it's the price passengers pay for bargain fares.
Information about "tariff/fare rules" can be found once buying it, but to save you time - with OeBB exchanges and refunds are not allowed (however did you consider switching to WestBahn on Vienna to Salzburg journey? Full WestBahn fare is not as expensive as full OeBB), with MAV SparDay/SparNight discounted tickets Budapest-Prague it's the same story - no refund or exchange (however MAV offers special tourist ticket for 49 euro, it is sold in unlimited numbers per departure, thus good for those who isn't sure about travel plans, because it's still much cheaper than standard full fare ticket), with CD discounted "First Minute Europa (Austria)" it's again no refund/exchange policy