I've wondered the same thing. Can the guards be "mapped" from their body heat? If there were hundreds of men in a cave, could their cumulative body heat be detected even though they're underground? Probably stupid questions, but I'd like to know. From space, not likely. But, there's no need to do it from there. Once the Air Force controls the air, drones can be used to do it from low altitude, with no threat to a pilot.
The earth is a big heat sink, so an underground heat source has to be very powerful or very close to the surface to become visible. But, ventilation shafts and escape tunnels will show up like flares on infrared, especially in the winter.
Exactly what we can do from space is classified. However, airborne IR imagers can certainly pick up vent locations from occupied tunnels. From open sources you will find that NASA has one manned IR imaging plane that flies at 50K feet. Once vents are located and attacked, the tunnels will be useless.
In addition, with high res visible imagery we will map all imnportant tunnel entrances. Software will tell us where to place a bomb or two for max effect.
They wont be using their tunnels for long. That's a fact.
These attacks will be so tramatizing to them -- I think we can knock out a few tunnels and then wait for the Bin Ladin organization in Afganastan to fall apart. That will not win the war but it is a good start.
