I'm not a Toast user, but there's a difference between an Audio CD and an MP3 CD. The format of the data on the disc is completely different. With an Audio CD, the format of the data is essentially a .WAV format, and the cross-fade option actually overlaps the music, and creates a new location for the start of the Track, and you can fit about 80 minutes of music on such a disc, and the tracks have a definite "order" when the disc is played. (Not that you can't use "shuffle" play, but you'll always here the overlap from the "previous" song in the original play order.)
An MP3 CD is a Data CD with MP3 files. You don't identify the order of playback when you create such a disc, and you can fit many hours of music onto the disc.
You should be able to create an Audio CD using MP3 files, at which point, the MP3 files are decompressed into the .WAV format, and again, the Audio CD is created with an anticipated playback order.
Not sure if that helps or not?