If the tubal ligation (cutting and sealing) has been done properly, then pregnancy by normal means is not possible. But now and then - very seldom - the surgeon doesn't get it right and a pregnancy...
The chance of pregnancy following tubal ligation (burning, cutting, clipping, tying) is very small - but since our body's are designed to heal - it occasionally happens. The chance of this happening...
Yes it is very possible. My sister is living proof of this. She is now pregnant for the second time after having her tubes tide and then redone after it failed the first time. And this is cut clamped...