In theory, recommendations shouldn't be shared with the candidates... but as always, there's the theory and the reality.
I asked a peer for to write a letter for me. I gave her some documents on how to do that, but she did not really know how to proceed. She said that she would prefer if we write it together.

. That was really good, because she is not familiar MBA admissions, so I could avoid bad mistakes.
And then, there's my other recommender: my boss. I have a good relationship with her, so I did not see it as a problem... until she sent me the letter at work a few hours before the deadline. I had meetings and customers calls so I just told her to send it to the Adcom. Only after that, I read it and I wished I hadn't. There's always a question on the candidate's weaknesses, and I think that letter is seriously going to hurt my chances of admission. I know it's good to receive feedback and even be critised. But to an adcom, there's the truth you recommender can tell and the truth she shouldn't tell. I am afraid that she wrote the truth she shouldn't tell.
Anyways, I think that a recommendation should be shared only if you have the possibility to have your say in the recommendation letter. If not, what's the point?