I've heard legal concerns for #1 (hadn't heard of other states where a mandatory evac would entail seizure of private vehicles/property, but that's the case in Louisiana). As for #2, I'd really like to know that one as well. They tasked the buses to only take people as far as the SuperDome, and then they stopped that at 6 pm.
I know -- someone has some explaining to do about buses not taking people out of New Orleans all day long and why we kept seeing pictures of the interstate coming into NO with no cars -- why not open at least one of those lanes as well.