I was thinking the same thing myself, and I went through and checked the other aspects of the UI. I thought it would be in the city_tier_success_dialog, which (I assume) updated once the tier was achieved. I found this section of code and tried to mimic it in the promotion tree,
var achievementArr = this.get('model.data.achievements');
var delay = 500;
for(var i = 0; i<achievementArr.length; i++ ) {
var achievementInfo = achievementArr[i];
var targetBlock = this.$('#' + achievementInfo.id);
if (targetBlock) {
this.$('#' + achievementInfo.id).css('visibility', 'hidden');
this.showAchievement(this.$('#' + achievementInfo.id), delay, achievementInfo.track);
delay = delay + 1000;
}
}
But when I tried using the getter, it failed at this.get(‘model.data.achievements’).