Even with a fully functioning warning system to detect quaked and the resulting tsunami would there be enough time to evacuate people?

The Maldives and the Andamen Islands are isolated so getting people off on ships and getting those ships well away from the coastline would be difficult.

With regards densley populated regions like Tamil Nadu and Sri Lanka just how many could be evacuated? Roads would become clogged ad nothing would move.

Yes a few more lives might be saved but the loss of life would still be unbearably high. We live a fragile existance on a fragile planet and nature is always ready to remind us of that.