Is there any difference in the turnaround time for scores for standby test-takers? If so, how much longer will it take to get them than it takes for normal scores?
It shouldn't take longer to get ACT standby scores. It took longer in the past because there was additional paperwork that had to be processed (you would turn in a physical standby request form at the test center because the process wasn't all online yet). You can expect to get your standby scores at the same time as everyone else who tested normally.
Source: http://www.actstudent.org/faq/delay.html (standby testing is not mentioned as a reason for scores to take longer)