The number of buildings that could conceal a tunnel on the US side of the border in San Diego is very limited. Just look at google earth. ICE/BP should be on a first name basis with every owner and tenant of these buildings and shouldn’t have to wait for search warrants and observers to report activities. Any legit business owner should be more than willing to allow access at any time.
It’s the Obama Admin’s newest high speed underground rail system. Doomed to failure, just like his above ground projects.