In our lore, we're using a mix of HLA and HL2 OTA.
Infestation Control Grunts are replaced with regular soldiers at this point, but the other HLA soldiers such as Ordinals, Chargers, and Suppressors still exist.
As for the way they speak, OTA players are granted a lot of freedom in terms of how they want to speak and act. If they want to talk like an HLA Grunt, they're free to. Do they want to play like a generic HL2 soldier? Go ahead.