I don't have any numbers for you, but it certainly was known to happen--deserters from both sides crossed No Mans Land throughout the war. Prisoners were taken after failed attacks, though usually not many.

As to the odds of any particular person making it...that really would depend on where they were, how wide the front was, how active the shelling, how clearly he was signalling his surrender, and the whims of the guys in the trenches on both sides.

That said, somebody caught between the trenches would be well advised to wait until nightfall, when moving around became much less dangerous. During the day, any motion would attract the attention of snipers and machine guns. At night, if one was quiet, one could wander around no man's land in relative "safety."