From: Rabbi Akiva Eiger
To: Unknown recipient
Rabbi Akiva Eiger proposes that while ChANA"N correctly reclassifies an absorbed piece as min b'mino (per the Rash), since ChANA"N for non-basar b'chalav prohibitions is only d'rabbanan, it is nullified in same-species mixtures and does not require two times sixty. However, for davar she'yesh lo matirin—where even rabbinic same-species prohibitions are not nullified—two times sixty is indeed required, resolving the dispute between the Rash, the Ri, and the Ran.
Source: Shu"t Rabbi Akiva Eiger §217