What i have learned in my month of experience with Match is:
1.- Tags have NOTHING, I repeat, NOTHING to do with a track being matched or not, absolutely nothing.
2.- The only thing that matters when matching a track is the audio fingerprint of the song, the waveform.
3.- Many times tracks that are on the iTunes Store do not get matched, but when you trim with a wave editor (Audacity, Audition, etc.) the last second or two, they get matched... I do not know why, but trimming the last seconds (mainly the silence at the end) gets the track matched, again, Tags or format (MP3, AAC, etc.) have nothing to do with a track getting matched, but the waveform.
4.- Many tracks do get matched, but in the store they are Mastered for iTunes, and when you open the info tab, the MFi badge does not show up, so even though the only track you are able to buy is a MFi, you get a non MFi when you match a track, for example:
I bought the Sgt. Peppers by The Beatles, ripped it and I matched it, it was matched no problem, but some tracks were MFi and some were not, so the non MFi were trimmed one or two seconds, and then they were matched with MFi versions.