Yup, there was an agreement in place that Kasparov could see the analysis that Deep Blue output. The outcome has never been decided, in my opinion, because of IBM violating the terms of the agreement.
When K requested it, he was put off. This went on, and I tracked it closely at the time, waiting for IBM to give it up. They kept saying they would, but never did to my knowledge.
Kasparov was concerned that IBM could encounter a bug, or simply a losing situation, and would have the chance to intervene with Deep Blue's calculations without anyone knowing. Deep Blue made more than one move that made Kasparov suspicious during the match. (Years later, humans interacting with computers was shown to produce much stronger results than just computers alone, even when the computers were much stronger at chess than the humans assisting them.)
Many Grandmasters have pointed out that at top-level matches, particularly world championships, psychology is the MOST important factor in deciding the outcome. This makes IBM's behavior all the worse, regardless of their reason.
(My friend Mike Valvo, now passed away, was the arbiter at the match http://www.computerhistory.org/chess/full_record.php?iid=stl... When I first met Mike, I said "There's something I always wanted to say to you!" He said "What's that?" and I said "e4" to which he responded "c5" and we proceeded to play a few moves of a Sicilian. Mike was one of a few people who had played and beaten Bobby Fischer in casual play.)