No one at an ordinary McDonald's would even notice such a device. Ergo this was not an ordinary McDonald's, but one with security people looking for cameras. Why would a McDonald's have security people looking for cameras? Possibly because it was a mafia front. If you wanted to launder money, a fast food restaurant in a popular location would be a good place to do it. The way the employees behaved is consistent with…
I've looked into how McDonalds franchises work before and have learned about money laundering from Breaking Bad: how would using a franchise make sense? McDonalds (and most other franchise businesses) run very tight ships with stock (and marketing): if a business sells 100 burgers McDonalds is going to know, it seems that if suspicions were ever aroused with this McDonalds all the IRS (or whatever the french tax auth…
Bars are traditionally popular for money laundering because everyone pays in cash, liquor has absolutely insane mark-up, and it's really easy to pour it down the drain. I imagine a fastfood restaurant would not work as well, but who knows.