In Alberta I had to get plates for a vehicle and had to keep them when I sold the vehicle (and the purchaser put their plates on to drive off). There are even regulations about how long you can have different province plates if you move leaving you technically with 2 plates for 1 vehicle (I think you're supposed to return the other plate to the original province but is more complex if you are moving around for short term work contracts of a few months and them coming back before the plate expires).

I just figured this is how people end up with license plates on their wall from their first vehicle etc.

However this is another aspect of my point - there is no clear uniformity on the relationship and handling of vehicle registration, plates, ticketing and enforcement. When things are poorly defined, you get inconsistent implementation and Bad Things(tm) happen as a result.

Considering just the wasted postage alone, thousands of dollars of public funds were wasted sending out obviously stupid and invalid tickets - totally avoidable if someone had stopped and thought about what they were doing.

Enforcement systems like this are always in danger of running away as a result and some schmuck being bankrupted or jailed (if states allow that) despite being able to demonstrate conclusively that they have done nothing wrong and are not responsible for any of the tickets. Public bodies are not good at admitting they are operating a fundamentally flawed system and it is always easier to ignore the small numbers of victims of their failure and hope no-one else notices. It does not take a lot of research to find examples of flagrant miscarriages of justice in these sorts of situations.