Block caching for logged-in users in D6 with node access control

The block caching in D6 core only works for logged-in users when there is no access control module active. The ability to cache blocks for logged-in users on a site using e.g. OG or some form of taxonomy access control would be a huge benefit.

I have a calendar block that takes ages to render (because of multiple long-term repeating events). Since it looks as if this module can cache blocks per-user, this would be ideal in my situation...

... if there were a D6 upgrade (which would I guess just need to address this specific issue).