I didn't find an Auburn standard for unconditional acceptance on the Auburn site -- it seems as if some of the college websites have become vague on specific numbers and post averages instead.
It was my understanding years ago that a potential freshman needed a 24 on the ACT for unconditional admittance to Auburn (don't recall the GPA).
According to the following stats, 37% of Alabama freshman and 18% of Auburn freshmen scored below this threshold (between and 18 and 23):
Auburn
Alabama
Honestly I was a little surprised that 37% of Alabama freshmen scored below a 24.
Other stats from above links concerning enrolled freshmen:
Auburn average ACT: 27
Alabama average ACT: 26
Auburn average GPA: 3.78
Alabama average GPA: 3.57
Auburn GPA of 3.75 or above: 56%
Alabama GPA of 3.75 or above: 41%