They're custom models; it's made of 3 models:
-Background & Level
-Health
-Mana
I've requested 2 background textures from my friend (the other side has different background texture), and the 20 level texts (numbers from 1-20) are made by me. The HP and MP bars are animated, they have 101 anims (took me a while to get it work). Their colors are all the way white; they're set via triggers (because certain heroes don't use mana, but something else)
It's fully controlled by triggers. Each time a hero enters the map, a new struct instance is created for it, the 3 dummy units are created, and the the instance is linked to the list. A periodic timer goes though the list time to time to refresh the values.
It's a quite simple system (or at least, it was for me), but for some reason people come for me time to time wondering how it works