My impression is that SMART was trying to be quiet zone-ready with new construction, but it's not their responsibility or even ability to enact them. Actual quiet zones under federal rules are the responsibility (and in part liability, once they're done) of the local government, and any crossing improvements needed for that are actually local responsibility too so to the extent that SMART installed stuff that makes quiet zones possible they were a gift from the railroad to the locals. Go to FRA and look at the quiet zone rules.