You can certainly try to negotiate with your dealer - best done in person - and even better if you've been a regular at their shop. But whether you are successful or not is entirely based on the relationship you have with them. Whether someone else has been successful is a moot point.
I'm betting that is a high stress point - and I can see how it wouldn't last. Definitely not a lifetime product. Unfortunately, I doubt fixing it is going to last (in this case). A better solution would be to use that piece to make a mold, then make the piece out of fiberglass. Also, examine to figure out why it cracked and you might be able to alleviate that - or at least lessen the chances moving forward.
EDIT... meant to add... trying a bumper fix is certainly a good idea and worth talking to the shop about. Who knows, maybe it would work. My doubts are that, one, the structure/stress of this is different than a bumper (I've done bumper repairs before) and, two, the bumper repair gets painted - this piece would need to be painted, as well - can that type of plastic be painted well enough to last?
