I see very little benefit for Apple.
IBM makes complex expensive software that people are still trying to get rid of in the enterprise. Apple doesn't need a sales force for iPads, most top execs have been demanding iPads for the last 2 years already, it's just IT that's slow to adopt it because they fear loss of control with BYOD.
Only upside here is stuff like Watson and the likes. I can see IBM providing back-end services to Apple but that's about it.