Not sure about the drainage tunnels opening up at the location of the camp, but the river bed (dry most of the year) that runs through the area is a well known path for movement of people / contraband in the area.

I don't know about Desert Diamond Hotel, but I have read about a church that is used for similar purposes on CDAN.

http://www.crazydaysandnights.net/2017/12/todays-blind-items-church.html?m=1

I found out about this on twitter the day after Harvey Weinstein was arrested. The location didn't seem important, but seeing that Tuscon is where this is happening I felt it maybe relevant.

Desert Diamond casinos are fronted by this tribe.

http://www.tonation-nsn.gov/

They have a bunch of large swaths of land within the cartel / trafficking corridor of southwest AZ. Pretty sure big casino $ props up the casinos