What specific issues does windows phone 8 have with id3 tags?

I couldn't give you a simple answer because the two things I thought of (ID3v2.3 ISO vs Unicode and YEAR=2013 vs YEAR=2013 09 04) are both visible in mp3tag, so you would have seen them already.

If you do find out what the difference is, please post back. It would be interesting to know.

Cheers,
David.