Good question, JReese.
Perhaps they use some easily strippable tape that they can leave down for a while. Obviously, I would think, that if it wouldn't interfere with the players during the course of a volleyball match, it wouldn't interfere with the basketball players during practice sessions. Guess when the seasons overlap, that the lines can be removed for basketball games. Would seem to be labor intensive if the lines were constantly being put down and then removed right away. That's my guess, for what its worth!