This depends whether the cable car company in question cooperates with the Swiss transportation networks and SBB would sell their tickets. At some places like Riederalp/Bettemeralp, SBB will sell tickets for the cable car connecting the valley floor with the village/resort, however tickets for the cable cars between the village and the mountain peaks have to be purchased locally.
Therefore simply try to get a valid timetable connection for your cable car journey in question in the SBB Mobile app or the SBB Webshop. If there is a ticket purchase option with a price displayed for that particular cable car connection, then you would obviously be able to use your Half Fare Plus credit for it.