You never have to sit around waiting for them to catch up to you or get in your vehicle, either, as the game often warps them to your position. They never die or get wounded so you don't have to run around saving them. They actually manage to kill enemies on a regular basis I never tried it but they could probably win a number of fights by themselves. It's regrettable that there's no option for co-op here but at least the companions aren't a hindrance.
You control one member of the squad while the other three are A.I. Yes, seems like the sort of thing you'd outsource to a group of soldiers who went AWOL. They're now working for the US military again and are entrusted with a mission that could decide the fate of the United States. In the first game, they had ditched their posts to steal a bunch of gold from a foreign military but those events are never mentioned in BC2. The two games at least have the same main characters, a group of wise-cracking AWOL American soldiers.
BF:BC2 is a continuation of the storyline from the first Bad Company, kind of.