An undefeated BYU team (with wins over multiple decent P5 schools - and at least big names) would usually go up for the last NY6 bid against schools that have THREE losses. 

Here's the list of NY6 at large selections since the NY6/CFP era

2018 - Michigan (10-2), Florida (9-3), LSU (9-3), Penn State (9-3)

2017 - Penn State (10-2), Washington (10-2), Auburn (10-3)

2016 - Wisconsin (10-3)

2015 - Ohio State (11-1), Notre Dame (10-2), Florida State (10-2) 

2014 - Baylor (11-1), Michigan St. (10-2), Arizona (10-3)