[quote name='shrike4242']Wait, why would you be sued over having liens on his property? He owes you money, so why are you getting sued over it?[/QUOTE]
My lawyer wife explained it to me, but I don't remember perfectly so I'm going to butcher this answer. But the gist is here.
It's a preliminary move on the part of the government. They can't sell a property with liens on it, so they sue to become the "primary" (or something like that). It allows them to seize it for first rights to the proceeds to a sale. It's their way of saying they're getting paid first, so we don't swoop in and try to demand money out of their pocket after the fact if the sale doesn't cover what's owed to both (or all) of us. The letter was CC'd to two other lien holders, so there's others too. A roofing company and an individual. They're not asking for money out of our pockets per se, they're just essentially cutting to the front of the line.