What do you mean "assuming iTunes would be able to match and/or upload them?" What's the criteria for music being matched or uploaded?
When iTunes Match goes through your library, it uses a three-step process in order to make the system more efficient. First, it scans your local song library, then it looks within the iTunes Store to see whether any of your songs match up with what's already on the server. If the songs are already on iTunes, the song is then deemed to be "matched," and it's not uploadedinstead, you simply get access to that song, via iTunes, on all of your devices. The third step only comes in if your songs are not matchable with anything that currently exists on iTunesin this case, the songs are uploaded from your computer to iCloud, and they count against the aforementioned 25,000 song limit.
Still, there are certain scenarios in which your obscure songs may not be matched or uploaded to iCloud. For example, songs that are encoded at a low bit rate (some are theorizing 96Kbps, or 128Kbps) are simply ineligible for iTunes Match and won't be uploaded at all. And even more maddening, as tweeted by Macworld's Dan Moren, songs that are only in Smart Playlists (and not in normal iTunes playlists) are strangely not eligible and therefore won't be matched. It seems if you want those songs to be matched or uploaded, you must remove them entirely from your Smart Playlists and add them to non-smart playlists to get iTunes Match to see them.