HalfLife2.net has interviewed some members of the Operation Everlasting Shadow mod.

Here's a snippet:

HalfLife2.Net: You're working with the Source engine, which is already renowned for it's realistic physics. Are there are gameplay elements you plan on implementing to take advantage of this?

Badger: As players of Opposing Force and Half Life will no doubt recall, the Black Ops did some spectacular moves in close combat... we are planning to use Havok to physically simulate arms and legs making contact, thus keeping clipping and other ugliness to a minimum.

you can read the rest of the interview here