I think you're safe. If you were taking birthcontrol pills, there is a chance that they might not be as effective while cleansing. That is only due to the Salt Water Flush and lax tea. Since you have actually had a tubal ligation (a permanent form of birth control) and you do not use birth control pills - you don't have that risk.
For those of you who are on the birth control pill, it would be good to use an alternate form of birthcontrol (condom or abstinence) to prevent pregnancy during your Master Cleanse.
My husband has had a vasectomy (another permanent form of birth control) and while I was on the Master Cleanse I did not get pregnant.