Ouch, this rocks hard enough to hurt my head. It hurt my head so much that...
Err...
If the post is imported from RSS from a WordPress blog AND is tagged already...
(You see where I'm going don't you?)
How can I use those tags as these tags?

Same server at least but tags may well be parsed in RSS using the plugin...
That would make it the ultimate. Hell, I'd worship the ground you walked on if you could do it. I might already.