I'm pretty sure in FoR Elites were encountered before what happens on Reach. That's why the Spartan II's have energy shields for at least the last half of the book. I could be wrong.
Nope, they get their shields from a reverse engineered Jackal gauntlet obtained during the raid (Chi Ceti) where Sam dies. That is why Spartan shields are a yellowish gold, and Elites have a bluish white shield.