Very Nice find Naku.
As for replacing the startup songs with this you could either look on google to try and find an answer or just go into the files and look around for the startup song files and replace. I know i would stay on the startup screen longer if this were my startup song lol.
tf2 uses a few files to play at the beginning so what you need to do is take the file and copy it 3 times, you should have 4 copies now. Leave the first named "gamestartup" and the rest ending with an ascending number.
ex: gamestartup, gamestartup2, etc. until 4
now go to your "tf" folder open the sound folder and create a "ui" folder then place your files there.