This came up on one of the SABR bulletin boards.
Their OPS differential for the whole season was .073. That translates into a winning pct of .592 using my equation Pct = .5 + 1.26*OPSDIFF. The Orioles had a differential of .096, good for a pct of .621. That means that the Orioles would have 53% chance of winning any given game using Bill James' Log 5 method. I came up with the Orioles having about a 56.5% chance of winning the series, taking into account all the different ways they could win a series of a given length. They also had home field advantage, which should have increased things about 2% (2% more than 55.7% so about 58%)
7.9% of the time it is an Orioles sweep
14.8% of the time the O's win in 5
17.4% of the time they win in 6
16.4% of the time they win in 7
So the Pirates had a 42% chance of winning