My main concern with the change to lists in the sideblocks is the semantics and naming. I strongly believe that good names must be chosen for classes, much like good variable names. Not that compilers or web browsers care, but other programmers/web developers do.
So seeing a ul (that is, an unordered list) with a class of list strikes me to be as confusing as an Integer called int, which may be fine if your writing mathmatical code where it really is just an integer but in most cases it will be a count or a total. In this case perhaps sideblockmenu would be more appropriate.
Similarly, the use of r1 and r0 never made much sense to me when used to markup tables, (I would have much prefered class 'odd' with 'even' being entirely optional, since 'even equals not odd') and there was in fact places in the tabs HTML that got r0 and r1 understandably confused (and may still be actually, I've not checked recently) which meant you had to have duplicate CSS for the same kind of tabs on seperate pages. So carrying this on to mark up list items, when the variable means row0/1 seems to invite double confusion.
Finally, using c0 and c1, which I believe stands for cell 0 and cell 1, to refer to spans is somewhat confusing. In addition, the icon could be put into the css as a background-image, which would allow zoom or high contrast themes to change both the image and its size (or postion, filetype etc.) with much greater ease than if it's hardcoded into the HTML.
Overall, I think it would be a shame if the effort to further accessify Moodle takes a narrow focus of replacing table cells with spans, rather than converting to more semantic code which would actually have a positive impact on far more users' experience of Moodle (whether they consider themselves to be in need of accessible software or not). I know the semantic code is more effort, and causes even more disruption, but I worry that once the automated accessibility checkers are satisfied and the 'accessible' tickbox has been ticked that real users will be left somewhat disadvantaged, with no external motivation to move things forward.