I tried FaderPort Classic to work with Cakewalk but failed. I installed FaderPort Classic driver and selected it from list of Control Surface but no response. I didn't try it for Sonar, probably was the same.
I tried FaderPort V2 by Mackie Control mode, it does work with Cakewalk, because FaderPort V2 doesn't come with Cakewalk mode from factory. I won't try FaderPort Classic by Mackie Control mode because it's meaningless for FaderPort Classic, a device which has specific Cakewalk mode.
Oh yes, there is a genius made an AZ Controller driver lets FaderPort Classic does work with Sonar (Cakewalk also maybe)
http://forum.cakewalk.com/AZ-Controller-has-made-the-FaderPort-awesomeAlphaTrack-is-on-the-way-m3209687.aspx