Re-check your math. 100 cars will hold less than 10% of the 100,000 people. No way you are going to get 1000 folks in a rail car. Try 1000 rail cars and 50 or 100 locomotives. And as I asked someone else in another post - where are you going to take them?
And you will never get a realistic answer to that question.
You are correct PAR35. You can get 10,000 to 15,000 out with about 100 modern passenger cars...enough to empty the Superdome in two or three round trips.
Where would they go? Lake Charles...perhaps Beaumont. Wouldn't get them ENTIRELY out of the storms path....but both locations should be much better off than NO.
As for shelters, the usual: gymns, churches, warehouses, Sam's Club, Costco...