Yes it is. Book via tickets.oebb.at. Do NOT use the "Seat reservation only” option but add the Interrail/Eurail discount and then look for normal tickets.

When doing this, there is only an option for “Global Pass”. Do you know if reservations bought like this can also be used with a one country pass if the trip is only within that country? For example a Germany pass to go from Basel to Hamburg.

Yes, that is possible. Just use "global pass"  as option.

But only for trips in the country where the pass is valid. For international trips you have to buy in that case the reservation + ticket in the country where the pass is noz valid at a ticket counter.