The problem with this is tunnels aren't as discreet in the modern day.
While satellites are often overhyped for tracking moving targets in real time (i.e ships), one of the things they are good at is change over time.
When you build a tunnel, the rocks and dirt have to go somewhere, and usually need dump trucks, etc. to haul out (which over time leave big, obvious tracks). Over time, specific sites build up nearby debris and you end up with visible tracks disappearing into a mountain.
To collapse such tunnels, even the smaller 2000lb - 5000lb bunker busters can do the job.