Using domain access with caching module like APC for all the (sub)domains

Issue Summary

I'm trying to figure out how to use APC with domain access module in my drupal 6.22 installation. I've been trying to accomplish this in two ways

• Using Cache Backport module with APC (Drupal 7-beta3)
• Using the authcache module with cache router module with APC

I'm using the cache backport module along with the APC module (beta3 version of 7 that's backwards compatible and patched to use $prefix). The APC is configured in the server properly and I've installed the modules and updated the settings.php accordingly to make sure cache backport and APC take effect.
From the APC panel data in the site and with basic load with apache benchmark, testing it's quite obvious that the caching is effectively working for the base domain (domain id 0) only and not for any of the other domains (but pages do not seem to be cached in any case though).

Using the second method of Authcache module combined with cache router adds one entry into the APC for each page hit but fails to use the cache entry for subsequent requests which is visible through the APC panel showing number of hits, recently updated time and the Authcache debug panel.
Commenting the domain/settings.inc from settings.php the Authcache appeared to instantly spring to life caching the pages and using them for subsequent requests. In both these cases the other items like menu items, content types etc. seemed to be properly entered into the cache.

Based on this link I got the domain settings to be included before the cache settings but this did nothing than to make the caching stop working altogether.

Some insight in this matter would be greatly appreciated.