ThisI’m really not sure you’re going to be able to make people talk to each other. Around half of the people will, and always will be, completely uncomfortable in that sort of environment and pushing that on them will only make things worse.
I would quite possibly spend the entire time plotting the early demise of anyone who forced me to do this.
I like socialising with people I like, I hate socialising for the purposes of networking.
There is an sort of anti-geek ethos in companies now, HR don't seem to understand that some people are not outgoing and feel completely at sea in these situations. They will no more benefit from the experience than being stabbed in the face with a fork to improve their morale.
What they want is to be appreciated for what they do and not to be made to feel like freaks for just wanting to do their job on their own.