I've never seen any actual statistics published by COMBANK regarding this. Your best bet is to just search through this thread and figure out a range on your own. Not the most helpful advice but it's the best you might get
I tried last year... they email back a generic 'if you score over xx%, you stand a xx% chance of passing' (what they have posted on their cover page. I think they request voluntary score reporting from those who've taken the test and will possibly give some correlations when they have sufficient data. It's still a relatively young Q bank.
I think QBank scores are usually poor predictors of performance. Your best bet is to take a practice test and see how you do. These are better at predicting actual performance at discrete points of time in your studying (i.e. QBanks are collection of test scores from many stages on many different subjects that might not reflect greatly on the actual distribution of questions on a real exam, etc.).
Also, I'm on my second UWorld pass and am averaging 85%. This is predicted from some sources to be above a 260. There is no way in heck that I'm even close to being at that point (i'm probably in the 220's/230's right now).
Its that high because on second pass on question banks you remember most of the answers so your mind just picks it without reasoning out the other choices sometimes. I would say if you scored a standard deviation above average you stand to get national average or above on COMLEX.