Can anyone point to a guide for homeowners facing a tax lien?

[Johann Jells]

My city is doing a long overdue revaluation and fearmongers are saying crap like "they'll take your million dollar house and sell it for the tax bill". My understanding was if your tax lien were sold at auction, if you didn't pay them off they could sell your house, but anything over the tax and fees would go to your bank and then finally you if there's anything left. They can't sell a $1m house with a $40k lien for $600k and pocket the whole thing. But some sources I saw said the mortgage is wiped out by a lien sale.  In practical terms this would never happen to a mortgaged property here because the banks hold escrow money and pay the taxes. Any clarification, or better yet a website or publication, would be appreciated.