Zero sum gain then....If they're on the lots you should now be able to buy from a California dealer.
NY: $42k MSRP Bolt -$2k NY Rebate = $40K Bolt
CA: $42K MSRP Bolt -$3k dealer discount = 39K Bolt + $850 to ship across country to NY + $39,850 Bolt
Net savings = $150!
The $2K NY Rebate is at the dealership, not through tax return- so you have to purchase the car at a NY dealership to get the $2K off the price of the car