Well, even Workshop in Moodle 2.x does not support exporting data yet. The tricky part is the format of the output data. I agree we must be able to produce them somehow so they can be post-processed statistically. However, we must provide a general solution for all types of the grading forms in the Workshop.
What I was thinking about was a unified format that would output the filled grading forms data as normalized values. What all grading forms have in common (regardless whether it is Rubric, Accumulative or whatever) is that they all consists of a set of assessment dimensions. The filled assessment is internally converted to a value from 0 to 100%. We could generate such report. So while data for the filled rubric would contain columns with values like 0.00, 0.25, 0.50, 0.75 or 1.00 (in case of a rubric with 5 columns), the Number of errors (Error banded in 1.x) would produce just one column with either 0.00 or 1.00 - depending on what the reviewer (grader) said.