I was billed for 407 for a deceased person as well. Same as the OP, they were going through the past logs and once I took over the plate, I had to pay or I could not use the plate or get a sticker for it. I could use my original plate. This was a vanity plate and I really wanted it for sentimental reasons.Once my home address received a 407 bill for a deceased family member that didn't drive, have a car or was alive at the time on the bill.
I tossed it away and a few months later received a letter saying it was going to creditors for collection and it will affect future credit ratings etc.
Just to shut them up I mailed them a copy of the bill and the death cert with a note that if they didn't straighten things out I was going to call the Toronto Star / Silverman helps .
Never heard from them again.
Come to find out that a family member drove the car before it was given to the person who it was willed to. So even though We had a death certificate, it was not accepted because they had proof of the car using the 407.
I paid the bill and finally got the money out of the family member. But I did get the interest taken off because 407 admitted this was the first bill they sent for the tolls. Can’t charge me interest on a bill I never got in the first place.