I'm far from an expert on this, but I would suspect the issue is less in the shape of the piers, but in the quality of the concrete work & materials. A "Y" shaped pillar is pretty standard practice. Hopefully Marigold is working to different specs, or at least checking in with TransEd as to what went wrong.
I'm sort of on the same boat here. Not an expert, but I have ordered a fair amount of concrete products through my work (structural and non-structural), and there seems to be something off about the "thermal expansion" reasoning they are giving. Concrete is such an engineered product. Maybe they ordered the wrong slump and or missed some additives or something? Having issues with 40% of your piers kinda seems like a major supply issue. Would be interesting to get a deeper look at the details regarding the issues.
Does anyone know how inspection/oversight works on a P3 like this? Id assume that the city should have some type of QA/QC/Inspection process? I'm pretty sure the City even employs concrete testers in their roadways division.