You could have tested this for us. I tried it and the answer is no. MC doesn't write TPUB tags.
MC supports many usual ID3v2 tags and some not so usual, like Band/Orchestra (TPE2), Composer (TCOM) or Conductor/Performer (TPE3), but it doesn't support all ID3v2 tags. Here is how I discovered that MC supports the Original Artist (TOPE) field too:
http://yabb.jriver.com/interact/index.php?topic=29081.0You can define any custom fields in MC, but naturally other applications don't understand them similarly in case the fields are defined to be saved in the MP3 files.
I don't need a full ID3v2 support. It is enough for me that the basic tags like, Artist, Album, Name, Track #, Genre and Year are used similarly with other applications. MC is my main tagger and database application. I never handle those special tags outside MC.
In any case I have a lot of files in my library that use other tagging standards, like APE tags, Vorbis comments, Windows Media tags or don't support any physical file tags, like wave, cue, video and document files.
I am quite satisfied with the situation, except that I still have not got a shortcut key and a toolbar button for the library backup even though I have requested them.
Please, JRiver.
Though, it wouldn't hurt to to check and perhaps add some ID3 mappings next time the MP3 plug-in is touched.