Where things seem to get messiest is if someone gets an 'advance' on what they'll receive in the will, except it's not written into the will so there is disagreement on whether they should get a full share or not.
Postal facilities often move >100k items a day. Or much more. Occasionally, a parcel will go missing, lose its label, be destroyed and unrecognizable, or end up in a place no one thought it was possible for something to fit. Thin items are especially bad for this.
There is only so much that can be done to try and follow it via CCTV and/or scans. Whether they have done everything practical, I don't know.
We don't machine sort passports (which reduces the chances of it getting lost/destroyed), but I think that's only new passports coming from the printers. Your passport may have been treated like any other courier item - assuming Canada's processes are similar.
The rest of it is probably a question for a travel sub.
No, but it does mean that basically everything built for standard domestic/commercial use is unsuitable and instead you have to use rail/marine/heavy-industrial grade equipment, and maintain it regularly.
If we expect to be remotely large, sorting by new only is infeasible.