Unfortunately it’s not possible to schedule your tags to play directly. However, there is another way to obtain the same result:
1) Create an automatic playlist in your music library
2) Click on add a criterion
3) Choose Tag > CONTAINS or EQUAL TO > enter the name of your tag
4) Don't forget to give your playlist a name before saving
Once that’s done, you can add your playlist to your Planning. Your playlist will automatically update itself when you add or remove MP3 files to your tag.