Hey!
At the bike kitchen in Vancouver we ask the client that if the bike is going to stay overnight that they remove the battery and take it away. We have a posting near the entrance of recommended local service centers for bikes we can't work on and e scooters.
We carefully assess any mechanical work to be sure we can actually do the mechanical. We also discuss that we aren't responsible for any electrical failure post work.
Lastly we make certain that a hub motor has a proper electrical coupling we can easily unplug.
As an aside we have Bosch and Shimano Steps certification but we haven't yet encountered the need to run any mid drive diagnostics.
Hope that helps!
Jesse Cooper