Er..CA's don't list tax liens..those are listed by the courts they were issued out of, or the state that issued them. Fed liens are tricky...I think they can remain indefinitely, or they can get renewed like judgments..
You can dispute them with the CRAs and when/if they get verified you can then request verification procedure..by law they have to get the info directly from the source...but it seems they like to use a third party and that is a violation....so you can nail the credit reporting agencies perhaps.....at the least they should tell you exactly where they came from.