I've tested them with teching and they are safe...
I mean to say that they are not the best option to use, and that they are not 100% safe. f2,3 is much safer than b1,2,1, and both knock the opponent outside bomb range. If you are going to set up a trait, always use f2,3 instead of b1,2,1. As for the other string, 1,1,2 is untechable, so it keeps the opponent in bomb range, unlike 2,u3 which can either be tech rolled or not, making some wake-ups using their invincibility to get through bomb and hit you when not teched, and some ranged wake-ups to hit you when they do tech preventing you from capatalizing on the bomb hitting. 1,1,2 does not have this problem, as most wake-ups lose their invulnerability by the time the bomb reaches them or cannot reach Harley. For example, Bane's venom uppercut when not teched after 2,u3 will hit Harley through bomb and launch her for some big damage.
However, I took a second look at 2,u3 when I got back from work since I've found a weird problem with bomb trait after 1,1,2 not connecting if you and your opponent share a stance. This is quite wonky, and only seems to affect floating characters and Hawkgirl when they use certain wake-ups. It can even lead to full combo against Harley simple because of stance. This really creates some problems as now it looks like there is no go to option to make sure bomb hits and keeps Harley safe, since 1,1,2 and 2,u3 can be punished.
I'll need to lab some more to see if there is a better option than those two.
