Here is some information I have found with regard to attempting to Avoid a Lien. Not specifically an IRS lien, mind you, because I am only researching information that is pertinent to my own case. But, hopefully you will find something useful in my collection.
"How To For Young Lawyers - Bankruptcy Rule 9014"
"How to Think About and Figure Out Whether A Lien Impairs an Exemption"
And here is an article that I ran across that explains how taxes are handled in bankruptcies. I cannot vouch for its accuracy, however.
Oh and also the Internal Revenue Manual contains valuable insight.
Good luck!