Is there a measure of how likely it is that a position will end in a draw? I was asked to rephrase this question. Hope at least someone gets what I'm trying to mean here now.

A position can be equal but asymmetrical. If it is very sharp and complicated then at least humans cannot overlook all options and a win has gotten more likely. That one be one kind of factor to consider for constructing such a statistical measure.

Would simply the width of the engine's positional tree be a useful measure? Would there be any interest in such a measure?

The players' personal inclination to draw as a matter of life long habit, or their need to win a point where a draw would still be a title loss, could be adjusted for in quantifiable and rational ways, since it is a statistic I'm asking for here, not a miracle prediction for one particular game yet to be played.

Is there a list of what combinations of openings have ended in a draw at top level? Would that be of any interest when trying to predict the outcome of any game?

Can all such things which appear to be of meaning for predicting  the outcome of games in general?

(I cant believe it is so very hard to explain with ever more words these obvious thoughts to people here who are supposed to be interested in Chess of all things).*
You have several questions which don't appear to be related. I'll answer you this one:


  Q: If it is very sharp and complicated then at least humans cannot overlook all options and a win has gotten more likely. Would simply the width of the engine's positional tree be a useful measure? 


Yes. There's a related concept known as positional complexity. Of course, the more complicated the position it is, the less likely it should end with a draw.


Using Heuristic-Search Based Engines for Estimating Human Skill at Chess has a definition for the complexity measure. Their definition is simple and straightforward. Computer Analysis of World Chess Champion is a similar paper.
Chess DB has a brief description
Who is the Master defines several more measures, they call them "conformance".
Another related: Intrinsic Ratings Compendium


If you require technical explanation, please edit your question and I'll update my answer.