Does engine score correlate with winning chances? I was wondering if there is a statistical or probabilistic (at least approximate) way of looking at a score of a chess position of a certain fixed engine, say "crafty version 5" for example. 

i.e. maybe +2 could be interpreted as "if the engine keeps on playing, 60% wins white, 30% black and 10% draw. I know this isn't the purpose of the score, but maybe it can be translated to approximate probabilities, maybe someone has done a statistical test with hundreds of games to see the correlation. And the amount of draw maybe depends on the "sharpness" of the position.
On the website of Houdini, one of the best chess engines (see for instance CCRL or CEGT), the author writes


  Houdini 4 uses calibrated evaluations in which engine scores correlate directly with the win expectancy in the position. A +1.00 pawn advantage gives a 80% chance of winning the game against an equal opponent at blitz time control. At +2.00 the engine will win 95% of the time, and at +3.00 about 99% of the time. If the advantage is +0.50, expect to win nearly 50% of the time.


The Chess Programming Wiki mentions a study where data from more than 400 000 computer games have been used to find a relation between pawn advantage (P) and winning percentage (W).


  W = 1 / (1+10^(-P/4))