I had no success either. I tried making my own ogg file and replacing 22_on_time.ogg with it, and it wouldn't play any sound at all. I tried different sampling rates with no luck.
I then took a sound from the Ringtones folder in system/media/audio/ and renamed it to 22_on_time.ogg and rebooted the phone. My thought was if I used another default sound file it would already be in the right format. Here's where it got weird. It started playing another audio file completely, one of my own files that was in my SD card media/notifications folder. It wasn't one I was playing with or had even opened. It literally just picked a random MP3 format file named SMSNew.mp3 and decided that was my new calendar tone.
In the end I gave up. I replaced the original 22_on_time.ogg file, rebooted, and now I'm back to the original sound.