I've attached Click to view attachment
the Python script I was using with MusicBrainz Picard. The beauty of this plugin was that it followed the New York Times Manual of Style in deciding what to make lowercase or not. After exploring this and a script I found online at http://liquidparallax.com/2007/10/19/mp3ta...ollection/#titl I've modified it and created a version that's in the same spirit of the original plugin.

For the most part you can look in the attached Click to view attachment
and you will find the lines where they specify lowercase characters to be nearly identical. So I just copied over the one from the Python script and replaced the one in the mp3tag script. It works fine and does what I was hoping for :-)

Thanks everyone for reading this thread, I got lucky and found a script I could adapt.

This was my modification if you want to have a look
Click to view attachment

You might want to have a look at this thread - as this uses MP3tag resources:
http://forums.mp3tag.de/index.php?showtopic=13185

I want to mention, that you have offered not a Perl script, but a Python script!

What have you tried so far on your transcription of the "New York Times Manual of Style" rules into Mp3tag Scripting language and where did you realize problems?

DD.20120507.2022.CEST

See above

Please attach the mta files (maybe zipped) to your forum post, not elsewhere on the internet.
Do I understand it right that you got all the mta rules running without any problem?
I would avoid to use the pseudo tagfield _ALL and use instead _TAG.

DD.20120507.2148.CEST

See above