Hmmm. Seems I celebrated too soon. Here's what I posted to the other forum topic.
So, I finally managed to get it to work with SWT using a bit of your method and trial and error.
What I have now is, it does not matter WHERE you place the code for the filters ( I could be wrong) as long as you do it as one of Ron's suggested ways; mu plugins, plugin network activated, plugin in child theme, functions.php on sub-blog theme.
See this Post on WPMUTutorials
I opted for the method to use it in the functions.php in the sub-blog theme.
Now comes the nearly tearing hair out part. Populating the posts works but remember its a CPT. You need to add support in the main blog (or tags blog) for the Custom Post Type.
I did that using the Custom Post UI plugin.
Soon as the CPT was created, I click it and there is the post already sitting there waiting. It was sitting in the DB waiting for a way to show up in the Admin Interface.
DoctorDR, does this give you any ideas to solve fro Post Formats. Is the Tumblog plugin installed on both sub-blog + main blog (or tags blog). Is Post Formats supported in sub-blog + main blog?
with CPT I had to add support for CPT must smn similar happen for Post Formats?
Sorry I'm sure you answered those ques already, tired, sleepy so forgive me.