On CB 13.0.51 and 14, you can try this:
var selTrackDA=page.mHostAccess.makeDirectAccess(page.mHostAccess.mTrackSelection.mMixerChannel)
var trackSelected=page.mHostAccess.mTrackSelection.mMixerChannel.mValue.mSelected
var trackSelectedCV=surface.makeCustomValueVariable("trackSelectedCV")
page.makeValueBinding(trackSelectedCV,trackSelected).mOnValueChange=function(activeDevice,activeMapping,value){
if(value==1){
//selected
var baseObjectID=selTrackDA.getBaseObjectID(activeMapping)
var objectUniqueName=selTrackDA.getObjectUniqueName(activeMapping,baseObjectID)
var trackType=objectUniqueName.replace(/\s?\d+$/, '')
console.log("type="+trackType)
}
}