Some years there are 3 at-large spots in NY6 bowls. Some years there is only 1 at-large spot in NY6 bowls. The at-large spots are given out based on final selection committee rankings.
Would have to beat out other at-large teams.
The top 4 teams go to the 2 playoff bowls of the NY6. Then Rose, Orange (except for ND), and Sugar always get teams from a conference tie-in if they are not the CFP semifinal bowls.
After all conference tie-ins are decided, then the next 1, 2, or 3 on the selection committee list get the at-large spot or spots.
If BYU ever got a NY6 bid as an at-large team not in the playoff, it would be to the Cotton, Peach, or Fiesta bowl in a year when that particular bowl is not a semi-final.
The contract with the Cotton, Peach, and Fiesta Bowls also runs out after 2019-2020, so maybe they will continue with the NY6 or maybe they would be replaced by another bowl. Those bids are expected to be awarded in 2018.
The overall contract with Rose and Sugar goes through 2025.