I didn't see a way to actually check the original file's bitrate... once converted (to WAV) it's of course uncompressed.
But doing the math:
137 minutes of music = 190 MB
8220 seconds = 1556480 kb
1 second = 189,35 kb
So the bitrate should be around 190 kbps. It's a huge step upward from the in-game MI1 music, but wasn't MI2's music uncompressed in-game? Still the Collection's tracks sound different than in-game... not only regarding arrangement (like in "Woodtick Suite"), but also instrumentation (the slap bass in MI2's opening is different from the one in the game). It might be worth compiling a complete soundtrack including these alternates. Also MI1 features a "flute less" main theme in the menu (which the Collection's launcher uses as well, although not complete), which should be included too.