We bring tupperwares when buying groceries for the meat, ham, cheese, fish etc and even if the cynic might say it's just a "feel good" action, well, I still put a lot of plastics in our recycle bin but we halved it since we started doing that (and some other trick). Yes, it definitely feels good.
I don't think containers that come from the customer are allowed behind the counter here for food safety reasons.
Here they put a sheet (that they would use anyway) on the scale to separate it physically from the container, and what enters the container doesn't leave it (or goes to the trash).
doesn't it add significant weight to the price ?
They simply adjust the tare weight in the scale and that's it. They do it anyway with their own 1-use plastic boxes or sheets.
I've never seen a meat counter employee re-zero the scale after putting a container or wrap on it. I do occasionally see them reading -0.1oz or something initially, presumably to avoid the need for the employees to zero it out each time they weigh something.
My feeling is that they have a few presets available for the containers they use, but it totally can be changed to a custom one.