Another Anon posted about a company in building 666 that built epcot and had other Disney ties. He was wondering if they could have built the tunnels from mexico.
Disneyworld in Fl has miles and miles of underground tunnels and basements (which is an engineering feat in FL. No one has basements due to the water table being so close to the surface.)
They have a multilevel basement structure.
If they can build this, they certainly could build some tunnels from Mexico to California
http:// www.messynessychic.com/2015/04/16/the-underground-world-of-tunnels-beneath-disney/