NTT Docomo recently published the results of compatibility checks with other domestic carriers. There is no mention of data, but if voice works, so should 3G data. This is because, as far as I know, Japan never used 2G GSM. So it works with 3G data and voice, or it doesn't work at all. As you can see the results are not surprising. Everything is compatible with SBM and hardly anything with Emobile.
I assume that as Docomo adds new handsets, this table will be updated.