Tamper detection won't prevent anything. It would just be an indicator that something appears to have happened.
The software load that is wiped every time is a first, and extremely basic, line of defence.
Realistically I'd hope the OS is on a SD card that they can literally take out and throw away after they have the data off (you can pwn the micro-controller on an SD card) - and replace with a freshly baked card.
Presumably if their sensors say the system has been cracked open, they don't just ship it out to another user. (And they could have many layers of sensors, telling them if it was just via damage (hitting it with a forklift) or someone really getting in.) Considering the potential downside, I'm sure they've done some work here.
The software load that is wiped every time is a first, and extremely basic, line of defence.
Realistically I'd hope the OS is on a SD card that they can literally take out and throw away after they have the data off (you can pwn the micro-controller on an SD card) - and replace with a freshly baked card.