My experience is that generally, yes, it is possible as I've done it. Now the but for me lies in the severeness of the trigger... I am convinced that in my case some could never change just because I would not take the risk (even though that does not make sense, even to me, because a trigger is a trigger and not the original trauma/person).
I think that it may well be possible to change the being a stressor around by setting up clear rules. I did that with my ex-husband and that worked well for me. To give you an example (my therapist at the time had suggested this): We said that either of us could use a certain object (a special stone in our case) to "say" something. W, hen it was put in a certain place in the apartment, it meant that the other one needed space (at home) and the other one would leave the one who put the stone there alone until they came back. Needless to say it is key to follow those rules. It may feel risky at first (fear of withdrawal of the other, just to mention one thing), but from my experience I can only recommend trying it. My ex-husband was a "copier", i.e. he copied my behaviour, so if I stuck to the rules, he would too (once he'd learned that I would). What I'm saying is, if you try, make sure that these rules do have their agreed-upon effect, and don't suddenly e.g. come up with an "emergency" that really isn't (we had said that we can approach the other if there's an emergency; it helps talking about the definitions of the words you use (what IS an emergency of the kind for which you can approach the other) beforehand).
Generally, as said, triggers can be done away with (as in the e.g. object doesn't trigger anymore but is neutral) and they can be turned into positives, in the sense that I had big trouble with a certain look (hair color, body posture, facial expression) of a man, but now I do have friends with those features and I don't even notice anymore and I just realized now because you asked that those triggers are gone and not neutral but replaced by good. (Sorry, difficult to explain...)