score:7
It does not cover all the regular buses in the country but postbus.at is the main operator and does operate buses you could use. Unfortunately, it's not a part of the national train company (ΓBB) and the website therefore also includes trains, which is why buses do not show up in the search results for this particular journeyβ¦
rome2rio is another site that's very nice for intermodal comparisons, and it seems that in this case the price would be approximately the same. (You will notice that the buses suggested by rome2rio can also be found on the postbus website, but only if you look for them one-by-one.)