Hi Dan,
The coaccessibility score is not quite any of those things... because cicero calculates the inverse covariance scores using graphical lasso on overlapping windows, we needed a way to reconcile the pairs that are calculated twice. We decided to do a mean of the output if the values shared the same sign (both neg or both positive) or NA if the values have different signs.
We don't have a way to assign significance in this context, however the higher the coaccessibility score, the stronger (more confident) the coaccessibility within a dataset (this was backed up by correlating back to various experimental methods in the original paper).
Hope this helps,
Hannah