A dealership can lock in rebates at the time of an order, but I don't think they can lock in a rate at the time of order. At least that is what I was told by multiple dodge dealerships.
It's dealer specific. Legally, they aren't bound to the rebate as the factory is the one that determines the incentives paid out. If those incentives dry up, then dealers can't very well honor them.
Still, many dealers, including the one I bought from, "locked in" the price and financing. See this as more of a promise than law. When I ordered, Chrysler had a special financing deal, but due to production delays, it took me 5 months to get the car. By then, the Chrysler Capital deal had closed. Still, the dealership had promised me a rate. They worked with other lenders to get the same or better rate, and they did. They also honored the price they quoted when I ordered.
So while they can't lock in a rate and be held to it in a court of law, dealerships absolutely can make promises to deliver on terms agreed upon. It just sometimes takes more work to get the numbers to work. Granted, things like quoting a Power Dollars savings likely couldn't be help up to a promise if Dodge canceled those out from under the dealership. That's a LOT of money ($7170 in my case). Luckily, that promo was still on