Umm...BTS are lizards that NEED to bask with heat and UVB from above, unlike snakes that get their heat from below. So they need to have a basking light.

It's not hard to get a good one, either. I got a simple floodlight bulb from Lowes and it's in a dimmer lamp (clamp lamp that has a built in dimmer knob). There's an Acurite thermometer in his cage and the outdoor probe is set on his basking tile. I simply adjust the intensity of the light until the spot is around 100.
And since blueys brumate over the winter (most of the time, at any rate) they don't need any other heat source.

The rack setup most likely was using Radient Heat panels...but no one I know in the BTS community would support keeping these guys without light heat in a cage. Several good keepers/breeders have stacking cage systems, but they all have built in basking lights.

Bottom line - the best way to ensure good health in a BTS is to keep them in a cage with basking light.