Pregnancy while tubes are tied


So I have a question.

Is it possible to get pregnant while your tubes are tied?

My mom got her tubes tied immediately after she had my little brother 6 years ago and after she divorced his dad, she met the love of her life and married my stepfather. Right now they're TTC and not having much luck. My mom is still young, 34. Is there a chance she could get pregnant without the surgery to reverse the tie? Any stories of experience or answers would be appreciated.