Any info is helpful.
What you say about their lien being junior to real estate tax liens is generally true. However, the IRS has very strict guidlines concerning the removal of their lien. It doesn't happen automatically and may not happen at all if you don't follow their routine. Some of the counties that have foreclosed their liens and taken the properties are not able to sell them free of the IRS liens if they did not follow the IRS guidelines. Anyone considering buying a property with an IRS lies should proceed carefully.