ruling on such intervention is reviewed only for abuse of discretion. Stone. First Union Corp., 371 F.3d 1305 (11th Cir. 2004) see also AT&T Corp. I. Sprint Corp., 407 F.3d 560, 561-62 (2nd Cir. 2005) ("[a] denial of permissive intervention has virtually never been reversed" because of the considerable discret