I'm not sure what game your mate was talking about but this exact thing was done in a user-made multiplayer mission called CTI (Capture The Island) for Operation Flashpoint (which is a tactical shooter/soldier sim) back in 2003 or 2004.
In CTI [http://community.bistudio.com/wiki/CTI], two teams (consisting of 9 players - 8 squad leaders and one commander), start at a random position on the island. The commander controls the Mobile Headquarters (a special armored vehicle based on either a M2A2 Bradley or BMP-2), and with it, he can build factories that produce soldiers, jeeps, trucks, APCs, tanks, helicopters and even fixed-wing aircraft. From these factories the squad leaders can buy what they need with their allotment of points. Points are awarded to the commander for destroying enemy vehicles, taking and holding the towns on the map, and salvaging wrecked vehicles. All of the towns on the map start out held by a third party, the Resistance, who are hostile to both sides.
CTI has also been adopted as an official game mode in OFP's de-facto sequel, Armed Assault.