I thought more on this and looked at some detail in the code, and it should be fairly easy (as a quick, not a perma thing) to separate out.
1. Copy the w3t_Posts table and name it w3t_EventData
2. DELETE FROM w3t_EventData WHERE B_Board not like 'calendar' (change this to keep only your calendar posts)
3. Copy the modified postlist.php and rename it eventlist.php
4. In the ubbthreads.tmpl write an "IF" statement that says if $Calendar='Y', then the <a href="{$config['phpurl']}/postlist.php?Cat=$Cat&Board={$forum[$c][$f]['Keyword']}"> url should point to eventlist.php instead of postlist.
This might be easier to install once this has had a few iterations with all of you...as we would have 4 separate php pages and a few tmpl pages...and the only UBBThreads page we would have to modify would be the ubbthreads.tmpl. Adding the w3t_Events would stay the same, and we would add a w3t_EventData in a fresh install.
I know I am missing something (passing $Calendar to ubbthreads is first in my head)...but I am sure this would be easy to figure out, and we could then modify this calendar add-on MUCH easier than trying to re-hack it every upgrade.
Thoughts?