Actually, I know that. I have been through the Ivy League process myself with three family members. At a time, I was almost an expert on the Ivy League Academic Index. The index is a formula derived from combining SAT scores and Class rank (GPA's play no role in it).
What they can do .... and have done to fend off other schools .. is to issue a "Likely Letter" that states that given evrything they know that the recruit is likely to gain admissions.
An interesting study was done a few years ago by a Princeton prof. He found that attending an Ivy school as a recruited athlete had no impact on the athlete post college career. Said another way, an Ivy League education isn't better than attending a State university for athletes in terms of the post college earning potential. They aren't as mart as their classmates who got in going the regular route and this shows up in their careers.